The Trump administration is considering whether to pull back military support for the C.I.A., including potentially taking back much of the drone fleet the C.I.A. uses, according to current and former officials. The shift could sharply curtail the agency’s counterterrorism efforts that were greatly expanded after the Sept. 11, 2001, attacks.

The administration is considering multiple options that could take effect as early as Jan. 5. One would reduce the number of Pentagon personnel sent to the agency — many of them Special Operation forces who work in the C.I.A.’s paramilitary branch. But other changes being considered would be far broader and more consequential, making it harder for the agency to work out of military bases, use the Defense Department’s medical evacuation abilities or conduct covert drone strikes targeting terrorists in hot spots around the world…

It was not clear why the Trump administration is pressing forward with their review, given that Mr. Biden could easily roll it back. Some former agency officers viewed the move as a last attempt by President Trump, who has long reviled the intelligence agencies over their assessment that Russia interfered to help his 2016 presidential campaign, to diminish the C.I.A.

The Pentagon is reviewing a 15-year-old memorandum of understanding with the C.I.A. with the aim of moving some personnel from supporting the agency to other posts, a senior administration official said. Some in the Pentagon believe the C.I.A. has been getting too many military assets and the Defense Department wants more say in their allocation.