The White House press secretary has contracted coronavirus and is experiencing mild symptoms – days after being with the US president.
Jen Psaki said she was last in contact with Joe Biden on Tuesday when she met him in the White House.
The pair were more than six feet apart and wearing face masks.
The president, who is tested frequently, received a negative result on Saturday, according to the White House.
Ms Psaki did not accompany Mr Biden on his trip abroad to Rome for this weekend for the G20 meeting and next to Glasgow for the UN COP26 climate summit.
The 42-year-old had planned to travel with the president but scrapped the trip just as he was about to depart for Europe after learning that members of her household had contracted COVID-19.
In a statement, she said: “Since then, I have quarantined and tested negative (via PCR) for COVID on Wednesday, Thursday, Friday, and Saturday.”
“However, today (Sunday), I tested positive for COVID.”
Ms Psaki added that she is only experiencing mild symptoms and stressed that she has not been in “close contact in person with the president or senior members of the White House staff since Wednesday”.
“I am disclosing today’s positive test out of an abundance of transparency,” she said.
White House staff and others travelling with the president have been undergoing frequent COVID-19 tests since before leaving Washington and are all fully vaccinated – many officials have also received their booster jabs.
Mr Biden got his booster jab on 27 September, shortly after federal regulators approved the third dose for many Americans.
He has instead been accompanied on his trip by principal deputy press secretary Karine Jean-Pierre.
Ms Psaki said she would return to work in person after completing a 10-day quarantine and she has tested negative.