'Ms. Troye is a former detailee and a career Department of Homeland Security staff member, who is disgruntled that her detail was cut short because she was no longer capable of keeping up with her day-to-day duties, ' added Keith Kellogg, Pence's national security adviser, who said Troye reported to him and never once expressed concern about the administration's response.
"Towards the middle of February, we knew it wasn't a matter of if COVID would become a big pandemic here in the United States, it was a matter of when", Troye said in the ad run by a group called Republican Voters against Trump.
Mr Pence said the former aide's remarks sounded like a disgruntled employee, while a White House spokesperson said her claims were not true.
'The truth is he doesn't actually care about anyone else but himself, ' she says.
When we were in a task force meeting, the president said: 'Maybe this Covid thing is a good thing.
Asked about Troye as he left the White House late Thursday for a campaign rally in Wisconsin, Trump said he had no idea who Troye is. "She was terminated. They didn't want her", Trump said. "She was proud to work in this administration until things went sour when she departed at the end", the official told CNN.
"I still have a lot of respect for the vice president", she said. "She was terminated", he said. "She was important to the team as a staff person to the Coronavirus Task Force, but I don't know what to make of what has come out recently".
President Trump listens as Vice President Mike Pence speaks during a coronavirus task force briefing at the White House in April.
The vice president's office released a copy of Troye's departure email, dated July 23 and addressed "Dear Task Force Members".
She joins a growing list of former Trump officials backing the Democrat, which includes Miles Taylor, former chief of staff at the Department of Homeland Security, and former White House communications director Anthony Scaramucci.
The group describes themselves as "a group of current and former senior USA government officials and conservatives - including from the Reagan, Bush 41 and 43, and Trump administrations - seeking to restore principled leadership in Washington, refocus the Republican Party's priorities, and fix the American republic". "I am voting for Joe Biden because I truly believe we are at a time of constitutional crisis".
NPR reached out to Troye through Republican Voters Against Trump, but she did not immediately respond to a request for comment.
Mr Trump has been stepping up efforts to win over voters ahead of the presidential election in November.
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