Aides to President-elect Joe Biden who are trying to arrange a smooth transition of power from the Trump administration have met resistance to their requests for information from some Pentagon officials, an official on Biden’s team said on Friday.

After Biden beat President Donald Trump in the Nov. 3 election, the Democrat’s team only began meeting with administration officials in late November to coordinate the handover.

Trump, a Republican, has refused to concede defeat and his administration only authorized cooperation with Biden on Nov. 23.

But some of Trump’s political appointees in the defense department have recently stopped cooperating, Yohannes Abraham, the executive director of Biden’s transition team, told reporters in a call.

“We were concerned to learn this week about an abrupt halt in the already limited cooperation there,” Abraham said.

Earlier on Friday, acting Defense Secretary Chris Miller said in a statement that some meetings have been rescheduled but none have been canceled or refused, saying the department and the transition team had agreed to a two-week pause in discussions over the December holiday period.

Abraham said no such agreement existed, and that he expects the Department of Defense to reverse the decision.

Separately on the call with reporters, another Biden official said the president-elect would get a get a dose of the COVID-19 vaccine on Monday.

Vice President-elect Kamala Harris will get a vaccine dose a week later, the official said, adding that the COVID-19 health crisis will likely lead some of the incoming administration’s White House officials to initially not work inside the building.