President-elect Donald Trump has asked roughly 50 senior President Barack Obama administration appointees to remain in their posts after his inauguration to ensure continuity in government, according to Sean Spicer, incoming White House press secretary.

The officials include the highest-ranking career officials at key national security agencies like the Pentagon and State Department.

Deputy Defence Secretary Robert Work and America’s third-ranking diplomat, Under Secretary of State for Political Affairs Thomas Shannon, will serve as acting chiefs of their agencies until successors for the top jobs are confirmed by the Senate, Trump’s spokesman said.

Trump’s selection for James Mattis, the Pentagon retired general, is expected to be confirmed on Friday shortly after the inauguration ceremony, along with John Kelly, a retired general, for secretary of Homeland Security.

Senate debate on Trump’s choice of Mike Pompeo, for the CIA boss, is expected to start on Friday.

It is unclear if Pompeo will receive an immediate confirmation vote.

At the State Department, Shannon will be in charge until next week as a senate vote on Trump’s choice for Secretary of State, former Exxon Mobil CEO Rex Tillerson, is not expected until Monday or Tuesday.

Also staying will be Brett McGurk, the Obama administration’s point-man for fighting the Islamic State group, Nicholas Rasmussen, the National Counterterrorism Center Director, and Adam Szubin, the Treasury Department’s top official for terrorism and financial intelligence.

Spicer said Chuck Rosenberg, the Drug Enforcement Agency administrator, and Susan Coppedge, the State Department’s ambassador-at-large to combat human trafficking, would be left in place for the transition.

The National Institutes of Health said its director, Francis Collins, was asked to stay on at least temporarily.

Republicans and Democrats are still negotiating over Trump’s nominees and Mattis and Kelly may be the only ones to make it through on Friday.