The decision was made to mitigate the COVID-19 risk and prioritise health and safety, and US Secretary of State Antony Blinken expressed by phone his deep regret to the foreign minister of Thailand.
US Secretary of State Antony Blinken on Wednesday cut short a brief trip to Southeast Asia, aimed at revitalising relations in a region where China's influence has grown, after a COVID
-19 case in the press corps accompanying him.
Blinken had been due to hold meetings in Thailand on Thursday but informed his Thai counterpart he would return to Washington to mitigate infection risks "out of an abundance of caution", a State Department spokesperson said.
Blinken and senior officials tested negative on Wednesday in Kuala Lumpur, Malaysia, where the journalist tested positive.
The trip to Southeast Asia was Blinken's first since President Joe Biden
took office in January.
The Biden administration has sought to shore up ties with a region that had become uncertain about US commitment during a period of perceived neglect under Biden's predecessor, Donald Trump
China expanded its influence in Southeast Asia, pushing investment and trade integration, at a time when Trump had withdrawn from a US-inspired Pacific trade pact that sought to challenge Beijing's economic clout.
In an address at an Indonesian university on Tuesday, Blinken laid out a strategy of boosting US infrastructure investment in the Indo-Pacific region and strengthening supply chains, while advancing treaty alliances and expanding defence and intelligence cooperation with other countries.
The speech took a swipe at the conduct of Chinese companies and "aggressive actions" by Beijing, which he said the region had grown increasingly concerned about. China's foreign ministry said Blinken was "drawing ideological lines".
Blinken and his senior staff have tested negative for coronavirus
at each leg of their tour, which started in Britain and included stops in Dubai, Jakarta and Kuala Lumpur.
Blinken gave a joint news conference on Wednesday with Malaysian Foreign Minister Saifuddin Abdullah and also met Prime Minister Ismail Sabri Yaakob.
The Malaysian foreign ministry said the individual who tested positive had been immediately quarantined, and had not participated in Blinken's program in Kuala Lumpur.