Train service between Heathrow Airport and central London was briefly disrupted on Wednesday morning because of a fire next to a track.

Trains linking Paddington Station with Heathrow’s Terminal 5 may be canceled or face delays of up to 30 minutes because of the fire, National Rail said in an incident report. It did not provide the exact location of the fire or what caused it.

Rail lines had reopened but the disruption was expected to last until 12 p.m. local time, National Rail said in an update.

Last month, a fire at an electrical substation knocked out power at Heathrow and forced the airport, one of the world’s busiest, to shut down for almost a whole day. The closure disrupted air travel for tens of thousands of passengers around the world.

There was no immediate comment from the London Fire Brigade and Heathrow Airport on the disruption reported by National Rail on Wednesday.

An 800-mile rail corridor stretching from Angola’s northern border to the Atlantic Ocean was former President Joseph R. Biden Jr.’s signature project in Africa, meant to counter Chinese influence and reshape America’s engagement with the continent.

When President Trump came into office this year, he quickly moved to dismantle decades of American aid to Africa, raising fears that the United States was pulling back from its commitments. The future of America’s involvement in the rail project was an open question.

But this week, the acting U.S. ambassador in Angola, James Story, gave the first indication that the Trump administration was on board with the project, the Lobito Corridor, which is expected to improve America’s access to minerals like cobalt and copper that are critical to the clean-energy transition.

Mr. Story, who arrived in Angola last October, is leading a delegation of more than a dozen, mostly Western envoys on a three-day publicity tour along the rail line, including visits with local politicians.

As Mr. Trump continues to craft his own Africa team, the tour offered clues to how he plans to shape his policy on the continent, and the ways in which it may align with or depart from Mr. Biden’s approach.

“The Trump administration is all about making business to favor the United States,” said Osvaldo Mboco, a professor of international relations at the Technical University of Angola in the capital, Luanda.

Although no Trump officials from Washington came on the tour, Mr. Story said the administration supported the effort. The purpose, he added, was to show international solidarity, look for investment opportunities and make clear that the United States and its Western allies are not walking away from the project.

The railway was initially completed in 1931, running from Angola’s border with the Democratic Republic of Congo — home to the world’s largest cobalt reserves — to the port city of Lobito on the west coast. China funded the rehabilitation of the line a little more than a decade ago.

Under the Biden administration, the United States committed about $4 billion to various projects along the corridor, including refurbishing the rail line, and developing mining and agricultural projects.

Mr. Biden pitched the corridor as part of America’s new approach to engaging with Africa — focusing more on commercial partnerships, rather than just aid and extracting natural resources. He saw it as an answer to China’s longtime engagement with African nations, which has resulted in the construction of new cities, airports, highways and shopping centers.

Biden administration officials said the railway would entice companies to build manufacturing plants nearby so they could transport goods, and would give local farmers a way to ship their produce.

It is unclear if the Trump administration will champion those broader economic benefits of the rail line or focus squarely on increasing American access to minerals.

“Is this just about the refurbishment of a rail or is it about investing in telecoms and alternative energy sources and food security,” said Judd Devermont, who was one of Mr. Biden’s top advisers on Africa.

The project’s ambitions already have been affected by some of Mr. Trump’s policies. An initiative meant to teach women better farming techniques, with the hope of increasing agricultural production along the rail line, was shut down after Mr. Trump defunded the United States Agency for International Development.

There are some early indications, however, that the Trump administration might be looking for business investments in Africa.

Ben Black, the president’s nominee to run the U.S. International Development Finance Corporation, which lends billions to overseas projects and has been one of America’s main funders along the Lobito Corridor, has said he wants to take an “investment-driven” approach to overseas spending.

Adam Cortese, the chief executive of Sun Africa, an American solar energy company with U.S. government-backed projects along the corridor and in Nigeria, said his engagements with Trump officials had been encouraging. The officials have expressed a desire to invest in developing Africa’s energy infrastructure, he said.

“They support production as long as it has to do with U.S. companies,” he said, adding that his company’s primary competitors in Africa are Chinese state-owned entities. “There certainly seems to be a lot of support for increasing U.S. competition with China.”

Although Mr. Trump has not explicitly expressed support for the Lobito Corridor project, Ricardo Viegas D’Abreu, Angola’s transportation minister, said this week’s diplomatic mission was a positive signal. Angola’s president has said that strengthening economic ties with the United States is essential to help his oil-rich country grow and diversify its economy.

“We feel that no major disruption has happened even on the transition to this new administration,” Mr. D’Abreu said of the progress on the Lobito project.

Ultimately, the benefit that Angola and other African nations get from doing business with Mr. Trump will come down to how those countries position themselves, said Mr. Mboco, the international relations professor. They will need to strike deals that include U.S. investment in manufacturing in Africa, rather than allowing Americans to just extract natural resources, he said.

“Africa needs to stop being the poor family member,” Mr. Mboco said.

Soldiers in Myanmar opened fire on a convoy of vehicles carrying relief supplies from the Chinese Red Cross for earthquake victims in the badly hit city of Mandalay, according to a rebel armed group in Myanmar.

The attack was the latest indication that the military, which seized power in a coup four years ago and is fighting a fierce civil war that has caused widespread suffering, would not stop hostilities despite last Friday’s devastating earthquake that killed at least 2,700.

In a statement on Tuesday night, Myanmar’s junta chief, Senior Gen. Min Aung Hlaing, said military operations will continue as “necessary protective measures” despite the earthquake.

The convoy came under attack by military forces using machine guns at 9:21 p.m. on Tuesday at Ummati village in Naung Cho township as it was traveling toward the central city of Mandalay, the Ta’ang National Liberation Army (TNLA) said in a post on its Telegram channel late on Tuesday. It did not say how many people were in the convoy or whether there were any fatalities or injuries.

As a result of the attack, the convoy had to retreat to Naung Cho, according to the TNLA. It said that it has stepped in to protect the convoy, ensuring that it continues its journey to deliver aid to those in need.

Myanmar’s military and the Red Cross Society of China did not immediately respond to requests for comment. China, which has close relations with Myanmar, was one of the first countries to respond to the earthquake, deploying search-and-rescue teams and sending about $14 million in emergency aid.

In the wake of the disaster, the National Unity Government, the shadow government in exile, and the Three Brotherhood Alliance, made up of three rebel groups including the TNLA, announced cease-fires.

But the army has continued to bomb parts of the country since the disaster. On Tuesday around 5.30 p.m., 38 young trainees of the Kachin Independence Army (K.I.A.), an armed group battling the military in northern Myanmar, were killed in an airstrike in Kachin State, according to Colonel Naw Bu, the spokesman of the K.I.A.

It is unclear why the Chinese Red Cross vehicles were targeted. But the attack underscores the chaos and challenges of delivering aid in a war zone. Since the coup, a total of 6,476 people, including pro-democracy activists and civilians, have been killed by the junta and pro-military groups, according to the Assistance Association for Political Prisoners, an advocacy group.

In recent days, international aid groups such as the World Food Program and UNICEF have entered Mandalay and the neighboring war-torn region of Sagaing, a stronghold of the resistance where desperate people say food and water are running out fast.

But locals in both places have said their attempts to help with search and rescue have been stymied by the military, which has blocked them from entering collapsed buildings and imposed curfews.

In recent weeks, China has been practicing unusual maneuvers off its southern coast involving three special barges. The vessels have linked up one behind another, forming a long bridge that extends from deeper waters onto the beach.

That feat has been a warning to Taiwan.

The vessels’ debut suggests that China’s People’s Liberation Army may be a step closer to being able to land tens of thousands of troops and their weapons and vehicles on Taiwan’s shores, experts say. Developing that capability has been a priority of China’s leader, Xi Jinping, in his quest to absorb Taiwan — either by negotiations or by war.

China has been conducting military exercises around Taiwan for years, including a new surge this week. But even as China’s drills have intensified, and its missiles, warships and fighter jets have advanced, many experts have doubted that the Chinese military could cross the Taiwan Strait with the speed and numbers needed for a successful invasion. Strong winds and currents for much of the year add to the dangers of trying to land on Taiwan.

If the new barges go into service, they could expand China’s options for where and when to land on Taiwan, making Mr. Xi’s threat of a possible invasion more plausible.

The vessels have been practicing in waters about 220 miles southwest of Guangzhou, the city where they were built. The barges have retractable, heavy-duty legs that work like giant stilts. The legs protrude from the deck when in transit and are lowered, when the vessels are in position, onto the seabed to steady the vessels against the waves. The barges then thrust out long extendable bridges, forming a 2,700-foot causeway that links the vessels together and connects to the shore.

Pictures from foreign satellites have shown the barges practicing with civilian Chinese cargo ships and ferries that could carry vehicles and people to be offloaded onto the causeway. China featured the barges on a recent program about military rivalry with Taiwan, warning that they could play a potential role in an attack.

“This equipment is a bridge and a port combined into one,” Wei Dongxu, a CCTV commentator on the show, said of the barges. Once China gains dominance in the skies and seas, he said, ships loaded with military vehicles could dock with the barges and unload the vehicles, enabling heavy combat equipment to land without touching the water. He said of the barges: “Once they appear, that means that the landing has scored a major victory.”

Some American commanders and officials have said that Mr. Xi has ordered the People’s Liberation Army to be able to take Taiwan by 2027. Mr. Xi has not said that China would definitely invade Taiwan, and there is debate about Beijing’s intentions, urgency and capabilities.

Crossing the Taiwan Strait could be perilous for China’s forces, even with more options for getting ashore. The United States could send forces to help Taiwan against China, raising the risk of war between two nuclear powers. Before any attempt by China to land in large numbers — possibly with the barges — the first wave of invading troops could face fierce fighting in the strait and on Taiwan.

But the three landing barges showed that China’s armed forces were rapidly developing ways to get over logistical hurdles of a possible invasion, said J. Michael Dahm, a retired U.S. Navy intelligence officer and co-author of a study of the new barges.

The barges work in sets of three — the longest barge, at 607 feet long, the shortest, 361 feet. The vessels’ legs, when lowered, pin the barges in place and can push the hulls up and above the water, for stability. Each barge also has a tower at the front, which can telescope out a bridge, connecting it to the next barge or to the shore.

The barges form a pier onto which ships that line up alongside the barges could disgorge vehicles. The vehicles could then drive directly along the pier to the shore.

Mr. Dahm said that he used to doubt that the Chinese military would meet Mr. Xi’s goal of readiness by 2027.

“I will tell you my mind has really been changed over just the last 12 to 18 months, seeing the scale of infrastructure and capability improvements that the Chinese have made,” such as the landing barges, he said.

The barges first came to public attention early this year, after H.I. Sutton, a defense analyst, reported that they were being built in a shipyard in Guangzhou.

The Times analyzed satellite imagery and marine traffic data that showed that several commercial ferries and cargo ships took part in the exercises. The commercial ships sidled up to the two larger barges farthest from shore, apparently practicing how to get in place to offload vehicles.

The satellite images did not show any vehicles actually being unloaded. But ferries and cargo ships that took part were of a kind built or modified to handle heavy armed vehicles, like armored personnel vehicles or even tanks, said Jason Wang, the chief operating officer of ingeniSPACE, a company that analyzes satellite images and other data, including about the Chinese military.

Taiwan’s western coastline, facing the Chinese mainland, has relatively few beaches or ports where landing is easy, and those areas are relatively well guarded. The barges would theoretically enable China to pick other areas on Taiwan’s coast that might be more difficult to land on but are less defended, from which to come ashore, several experts said.

“These barges will open up new locations to deliver troops and material for Xi Jinping to choose from” along Taiwan’s coast, Mr. Wang said. He estimated that in one day the barges could offload hundreds of armored vehicles.

“China still doesn’t have enough gray hull naval ships to assault Taiwan’s main island on their own,” Mr. Wang said, referring to the typical color of warships. But when you add specialized dual-use ferries and cargo ships, “then that becomes a different story,” he said.

“You’re then starting to have enough vessels to be able to deliver a battalion on shore quickly,” he said.

Chinese military planners have closely studied previous wars involving amphibious landings, including Britain’s war to retake the Falkland Islands in 1982, and the D-Day landings at Normandy in 1944.

China may be some way from having a surefire solution to landing on Taiwan. The People’s Liberation Army seems likely to further test the new barges in larger military drills, possibly later this year, said Chieh Chung, a researcher at Taiwan’s Institute for National Defense and Security Research, a government-funded group in Taipei.

“They usually carry out testing through exercises before officially entering into mass production,” he said of China’s military. “Their direction is set — how to overcome all the difficulties that could trouble a joint landing operation.”

During the recent practice runs, it took several hours for the transport ships to dock at the mobile pier, even with help from tugboats. On March 25, one ship appeared to abandon its effort to dock at the pier where two other ships were already berthed. It succeeded the next day and was joined by a small tanker used to refuel the self-propelled barges, making for a total of four ships moored at the same time — a first for the formation.

Mr. Wang, the expert on satellite image analysis, said that at the shipyard in Guangzhou that built the new barges, another set of three was nearly finished and had entered the water for initial tests.

Robin Stein contributed reporting from New York.

Lawyers for Venezuelan migrants accused of being members of a violent street gang asked the Supreme Court on Tuesday to continue a temporary block on President Trump’s use of a wartime powers law to send hundreds of people to a prison in El Salvador.

The Trump administration has asked the justices to intervene and lift a block on the deportations imposed by a lower court. But a brief filed on behalf of the immigrants by the American Civil Liberties Union and Democracy Forward said that block is now “the only thing” preventing the Trump administration from sending immigrants “to a prison in El Salvador, perhaps never to be seen again, without any kind of procedural protection, much less judicial review.”

The government has already sent more than 130 Venezuelan men from the United States to El Salvador, according to the court filing, where the migrants “have been confined, incommunicado, in one of most brutal prisons in the world, where torture and other human rights abuses are rampant.”

The legal battle over the deportations of the Venezuelan migrants is one of the first major tests of Mr. Trump’s flurry of executive orders to reach the high court. It is perhaps the most high-profile of the eight emergency applications filed by the administration, focusing squarely on a collision between the judicial and executive branches.

There are typically no hearings or oral arguments for cases on the Supreme Court’s emergency docket, and there is no public schedule for a decision.

The 514-page filing, which included documents from the lower court and declarations from human rights experts, marks the latest turn in the legal fight over Mr. Trump’s efforts to remove immigrants accused of being members of Tren de Aragua, a street gang with roots in Venezuela’s northern Aragua state.

The Trump administration asked the Supreme Court on March 28 to to vacate a decision by Judge James E. Boasberg in the Federal District Court in Washington to temporarily pause deportations under the Alien Enemies Act of 1798, a law that gives the president sweeping authority to remove citizens of foreign countries determined to be “alien enemies” in cases of war or invasion.

In its application to the justices, lawyers for the Trump administration argued that the president was authorized to use the act to deport the Venezuelans because he had determined that thousands of gang members had “illegally ‘infiltrated’ the country” as part of a plan by the Venezuelan government to destabilize democracies.

Lawyers for the immigrants sharply disputed this, arguing that Mr. Trump was contorting the law in an “effort to shoehorn a criminal gang” into the wartime law “on a migration-equals-invasion theory,” which they argued “is completely at odds with the limited delegation of wartime authority Congress chose to give him through the statute.”

Last month, the Trump administration ordered the deportation of more than 100 people who the government argues are members of the gang. Since then, they have been denied any due process to challenge the allegations against them.

In their court filing, lawyers for the Venezuelans argued that keeping Judge Boasberg’s temporary block on the deportations would not present a risk to public safety, since the judge had not ordered anyone to be released nor prevented the government from deporting migrants under normal processes.

They cited a March 31 social media post by Secretary of State Marco Rubio stating that the U.S. military had sent another 17 people, some of whom he said were members of Tren de Aragua, to El Salvador. The Trump administration has claimed that those men had been deported under regular U.S. immigration law, not the Alien Enemies Act.

If the court were to lift the block and allow deportations to resume under the Alien Enemies Act, lawyers for the immigrants argued, the consequences could be severe. They said their clients would “suffer extraordinary and irreparable harms — being sent out of the United States to a notorious Salvadoran prison, where they will remain incommunicado, potentially for the rest of their lives, without having had any opportunity to contest their designation as gang members.”