By Phil Stewart and Idrees Ali

WASHINGTON (Reuters) – U.S. President Donald Trump said on Monday that he had “terminated” Defense Secretary Mark Esper, appearing to use his final months in office after his Nov. 3 election defeat to settle scores within his administration.

Trump, who publicly split with Esper in recent months over a range of issues, said on Twitter that Christopher Miller, director of the National Counterterrorism Center, will become acting secretary of defense. The Senate would be highly unlikely to confirm any new nominee before Trump leaves office in January.

“Mark Esper has been terminated,” Trump said on Twitter. “I am pleased to announce that Christopher C. Miller, the highly respected Director of the National Counterterrorism Center (unanimously confirmed by the Senate), will be Acting Secretary of Defense, effective immediately.”

The Pentagon had no immediate comment.

Esper had long been preparing for the prospect of his resignation or dismissal following the Nov. 3 election, particularly if Trump were to win a second term in office, sources said.

Trump has steadfastly refused to acknowledge his election loss.

Esper angered Trump particularly by opposing Trump’s threat to use active duty troops to suppress street protests over racial injustice in the United States during the summer.

Esper also disagreed with Trump’s dismissive attitude toward the NATO alliance, sources said.

(Additional reporting by Daphne Psaledakis and Susan Heavey; Editing by Tim Ahmann and Cynthia Osterman)