WASHINGTON - US Vice President Mike Pence's spokesperson, Katie Miller, tested positive for the coronavirus, President Donald Trump confirmed Friday.

Calling the person in question a "press person," Trump said during a meeting with congressional Republicans that "Katie, she tested very good for a long period of time and then all of a sudden today she tested positive."

"She hasn't come into contact with me," Trump said, referring to Miller, wife of his senior adviser and speechwriter, Stephen Miller. "She's spent some time with the vice president."

The president said Pence knew about Miller's infection and "has done what he has to do."

White House Press Secretary Kayleigh McEnany said during Friday's briefing that a member of Pence's staff had been infected with the virus, without identifying who exactly the person was.

The diagnosis of Miller, 25, delayed Pence's flight in the morning to Des Moines, Iowa, as six staffers disembarked the plane due to close contact with her, according to U.S. media reports. Two journalists were also summoned to the White House for a rapid test.

A senior administration official reportedly informed the media on Air Force Two, before Miller's identity was revealed, that "the vice president and the president have not had contact with this person recently."

Miller's positive test came just one day after she tested negative. Trump and Pence also tested negative for the virus Thursday, following the confirmation that a personal valet to Trump tested positive.

Miller's infection with the coronavirus raised fresh concerns about possible transmission of the contagion among senior administration officials. Trump, however, said he was not worried, adding that "strong precautions" had been taken in the White House.

Miller is the second staffer in Pence's office to test positive for the virus after an aide's positive test in March.

McEnany said at the press briefing Friday that measures are in effect to keep the virus from spreading among staff.

"We have put in place the guidelines that our experts have put forward to keep this building safe, which means contact tracing - all of the recommended guidelines we have for businesses that have essential workers we are now putting in place here in the White House," she said.

Trump told reporters Thursday that he would be tested for the coronavirus daily.