US President Joe Biden tested negative for Covid-19 just before the Cop26 climate talks got underway on Sunday, the White House said on Monday.
Mr Biden took the test independently of White House Press Secretary Jen Psaki, who on Sunday announced she had tested positive for the virus.
The test was required for the president to enter Britain, where Mr Biden has travelled for the global climate summit in Glasgow, Scotland.
Ms Psaki, who is experiencing mild symptoms, said she was last in close contact with Mr Biden on October 26 and that they were more than two metres apart and wore masks.
She is unlikely to have infected the president with Covid-19, CNN reported on Monday.
“Based on the timeline of Ms Psaki's testing negative for multiple days following her last encounter with President Biden, it is virtually impossible for her to somehow have infected the president,” CNN medical analyst Dr Leana Wen said.
Mr Biden had previously tested negative for the disease on Saturday, the White House said.
The White House press secretary did not travel with the president to Rome, which he visited before flying to Glasgow on Monday.
She had planned to accompany Mr Biden but cancelled after learning that members of her family had contracted Covid-19.
Ms Psaki said she intends to return to work in person at the end of her 10-day quarantine following a negative Covid test.
The president is scheduled to return to the US on Wednesday, when his social-spending and infrastructure bills may be voted on in the US House of Representatives.