KUALA LUMPUR, Malaysia — Secretary of State Antony J. Blinken cut short his trip to Southeast Asia on Wednesday after a journalist traveling in his delegation tested positive for the coronavirus.

A State Department spokesman said Mr. Blinken has tested negative at every stop on diplomatic visits over the past week to Britain, Indonesia and Malaysia. He had scheduled meetings for Thursday with senior officials in Bangkok, the Thai capital, but canceled to return to the United States.

He did stop in Bangkok briefly to pick up flight crew for his trip back to the United States on Wednesday night.

Ned Price, the State Department spokesman, said Mr. Blinken had called the Thai deputy prime minister, Don Pramudwinai, to “express his deep regret” over the change in plan.

“He explained that in order to mitigate the risk of the spread of Covid-19 and to prioritize the health and safety of the U.S. traveling party, and those they would otherwise come into contact with, the secretary would be returning to Washington, D.C., out of an abundance of caution,” Mr. Price said in a statement as the delegation was leaving Kuala Lumpur.

It was Mr. Blinken’s first trip to Southeast Asia as secretary of state, and his itinerary was meant to portray the United States as a more reliable ally to nations here than China, the regional heavyweight. The economic competition between the United States and China, which has led to tense diplomatic relations, has been one of President Biden’s major foreign policy concerns.

The administration is preparing a broader strategy for strengthening its role in the Indo-Pacific region, and Mr. Blinken’s travels this week had sought to assure Southeast Asian nations that they would remain a key part of that.

The journalist who tested positive for the virus was part of the small group of news media personnel who travel with the secretary of state. The journalist, who was not identified for privacy reasons, tested negative in Jakarta on Monday but then received a positive test for the virus after arriving in Kuala Lumpur, the Malaysian capital, on Tuesday night.

Foreign governments have stepped up testing requirements for traveling diplomatic delegations as the Delta and Omicron variants have surged around the world.

Mr. Price said the journalist who tested positive would remain in Kuala Lumpur for mandatory isolation while the rest of Mr. Blinken’s entourage traveled on.

Mr. Blinken invited Mr. Pramudwinai, who also serves as Thailand’s top diplomat, to visit Washington “at the earliest opportunity,” Mr. Price said. He also pledged to travel to Thailand as soon as possible.

On Wednesday, Mr. Blinken met with Prime Minister Dato’ Sri Ismail Sabri Bin Yaakob and other senior Malaysian officials in meetings in Kuala Lumpur, with only a few aides in attendance, to discuss security, economic and cultural issues, as well as coronavirus response.

He also met with Malaysia’s top energy official, and he took questions from reporters with the foreign minister at a news conference.