President-elect Joseph R. Biden Jr. said on Monday that his transition team had faced “obstruction” from the Defense Department, raising new concerns about the Trump administration’s cooperation with transition officials with just over three weeks until Inauguration Day.

“Right now, we just aren’t getting all the information that we need from the outgoing administration in key national security areas,” Mr. Biden said in Wilmington, Del., after he and Vice President-elect Kamala Harris were briefed by members of the transition’s agency review teams for agencies dealing with national security and foreign policy, like the Defense and State Departments.

In a statement on Monday, the acting defense secretary, Christopher C. Miller, defended the department’s level of cooperation with the Biden team.

A week before Christmas, Yohannes Abraham, the executive director of the Biden transition, said that the president-elect’s team had encountered “isolated resistance in some corners, including from political appointees within the Department of Defense.”

And last week, during an event at which Mr. Biden criticized President Trump for playing down the Russian hacking of the federal government and private companies, Mr. Biden said, “The Defense Department won’t even brief us on many things.”

But even as Mr. Biden complained on Monday about a lack of cooperation from some political appointees in the Trump administration, he also offered praise for career federal government employees who have worked with members of his transition.

New York Times