The expected withdrawal of McCusker's nomination in the wake of President Donald Trump's impeachment acquittal was first reported by the New York Post last month. Trump was impeached by House Democrats on charges that he abused his power by delaying the aide to pressure Ukraine to investigate his political rivals.

The move comes as Trump and his allies seek to root out members of his administration they view as disloyal following the president's acquittal. Most recently, the White House ousted Pentagon policy chief John Rood. Trump also removed Army Lt. Col. Alexander Vindman from his job on the staff of the National Security Council and recalled Gordon Sondland from his post as ambassador to the European Union. Both Vindman and Sondland testified publicly in the House impeachment probe.

It is unclear if McCusker will continue to serve in her current role. The Pentagon did not immediately comment.

A confirmation hearing would have given Democrats a rare opening to grill an administration official with some knowledge of the Ukraine aid deliberations after they were rebuffed in their efforts to subpoena additional witnesses and documents in the impeachment trial.

McCusker featured prominently in emails, published by The New York Times and Just Security, that showed the acting Pentagon comptroller expressing concerns over the legality of White House moves on Ukraine aid.

Unredacted emails published in January by Just Security between McCusker and Michael Duffey, an official at the White House Office of Management and Budget, show her rejecting a White House talking point that said OMB wasn't blocking the aid.

In another exchange published by the New York Times in December, McCusker pushed back on Duffey when he suggested the Pentagon, not the White House, would be at fault for a potential breach of budget law.

"You can’t be serious. I am speechless," McCusker replied.

The Government Accountability Office ultimately concluded the White House broke the law with its hold on the Ukraine money.

McCusker was formally nominated for comptroller in November, a post she'd held since David Norquist was confirmed to be deputy secretary in July. She was confirmed to be deputy comptroller in 2017. Before that, she worked as a Pentagon civil servant and as a Senate Armed Services staffer.

Senate Armed Services Chairman Jim Inhofe (R-Okla.), a close Trump ally, had initially planned to move quickly to advance her nomination and fill the senior vacancy. Following the New York Post report that the president may withdraw the pick, the Oklahoma Republican said he hadn't heard of any change in her status and wouldn't weigh in with the Trump administration.