WASHINGTON — 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.
“It’s nothing short, in my view, of irresponsibility,” Mr. Biden said.
In his remarks, the president-elect said that his team had “encountered roadblocks” from political leaders at the Defense Department as well as at the Office of Management and Budget. Mr. Biden emphasized the importance of a smooth transition, saying, “Right now, as our nation is in a period of transition, we need to make sure that nothing is lost in the handoff between administrations.”
“My team needs a clear picture of our force posture around the world and our operations to deter our enemies,” he continued. “We need full visibility into the budget planning underway at the Defense Department and other agencies in order to avoid any window of confusion or catch-up that our adversaries may try to exploit.”
In a statement on Monday, the acting defense secretary, Christopher C. Miller, defended the department’s level of cooperation with the Biden team. He said the department was continuing “to schedule additional meetings for the remainder of the transition and answer any and all requests for information in our purview.”
“Our D.O.D. political and career officials have been working with the utmost professionalism to support transition activities in a compressed time schedule, and they will continue to do so in a transparent and collegial manner that upholds the finest traditions of the department,” Mr. Miller said. “The American people expect nothing less, and that is what I remain committed to.”
The Biden transition was hamstrung at the outset by the Trump administration’s delay in formally designating Mr. Biden as the apparent winner of the election. The head of the General Services Administration did not take that step until Nov. 23.
More recently, Mr. Biden and his team have complained about their dealings with the Pentagon in particular.
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.” He expressed concern about what he described as “an abrupt halt in the already limited cooperation there.”
Mr. Miller had cited a “mutually agreed-upon holiday pause,” but Mr. Abraham said that no such agreement had been made.
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.” The department responded by calling that claim “patently false.”
After Mr. Trump’s postelection firing of Defense Secretary Mark T. Esper and a purge of the department’s senior leadership, the Pentagon was put under the political control of several Trump loyalists, including Kashyap Patel, Mr. Miller’s chief of staff, who is best known for his efforts to discredit the Russia investigation when he was a Republican congressional aide.
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. “For some agencies, our teams received exemplary cooperation from the career staff,” he said.
Mr. Biden also offered a downbeat assessment of the toll that four years of Mr. Trump’s presidency had taken on the country’s national security apparatus.
“The truth is, many of the agencies that are critical to our security have incurred enormous damage,” the president-elect said. “Many of them have been hollowed out — in personnel, capacity and in morale.”
Mr. Biden has emphasized a promise to rebuild alliances and restore the United States’ standing in the world, and he has already named most of his top foreign policy and national security officials — though he has yet to announce his choice to lead the C.I.A.
Since winning the election, the president-elect has had calls with a long list of foreign leaders, and in his remarks on Monday, he reiterated his desire to repair relationships that had been damaged during the Trump administration.
“Right now, there’s an enormous vacuum,” Mr. Biden said. “We’re going to have to regain the trust and confidence of a world that has begun to find ways to work around us or work without us.”
Michael Crowley contributed reporting.