US President-elect Joe Biden has alleged that agencies critical to US security have suffered “enormous damage” at the hands of the Trump administration.
Mr Biden said his team is not getting the information it needed, including from the Department of Defence, as it makes its transition to power.
He was speaking after a briefing by national security and foreign policy aides.
Mr Biden takes office on 20 January but President Donald Trump has refused to accept defeat in November’s election.
For weeks after the election, Mr Biden was blocked from receiving key intelligence briefings, an essential and normally routine part of a presidential transition.
Following Mr Biden’s remarks on Monday, Acting Defence Secretary Christopher Miller said officials have been working with the utmost professionalism to support transition activities.
A spokesman said the Pentagon has been completely transparent with the Biden team.