Republican senators had privately pushed the Trump administration to nominate a national security professional for the post, and advisers made clear that the president was not nominating Mr. Grenell for the permanent job. Mr. Trump has installed acting leaders in other top government vacancies, giving him freedom to maneuver around the demands of Senate confirmation.

By law, the current acting director of national intelligence, Joseph Maguire, has to give up his temporary role before March 12. Mr. Grenell is expected to begin his new job on Thursday. Mr. Maguire, in a statement on Wednesday, thanked Mr. Trump and said that when he was confirmed by the Senate to lead the counterterrorism center, he “never imagined what would follow.”

Mr. Trump can choose any Senate-confirmed official to replace Mr. Maguire, who has served as the acting director of national intelligence since the resignation last summer of Dan Coats, a former Republican senator from Indiana. Mr. Grenell was confirmed by the Senate for his current job after a delay caused by parliamentary tactics that stirred a bipartisan outcry.

He would be the latest in a line of intelligence directors who have had varied policy experience including diplomatic or military backgrounds rather than stints in the intelligence world.

But Mr. Grenell is also an acerbic combatant who throws regular punches at “fake news” reporters and Mr. Trump’s opponents online. Last month, he angrily demanded The Washington Post retract a report, which he insisted was based on fabricated sources, that Mr. Trump had threatened to impose auto tariffs on European cars if European leaders did not adopt a tougher line on Iran’s nuclear program. The next day, Germany’s defense minister publicly confirmed it.

Mr. Grenell honed his combative style when he worked as a spokesman at the United Nations for the former ambassador John R. Bolton. Often to the surprise — and sometimes the horror — of the State Department’s more staid communications officials who worked for Secretary of State Condoleezza Rice, Mr. Grenell would take on reporters and argue long into the night about stories appearing in major newspapers and on television.

In recent days, after Attorney General William P. Barr said in an interview that Mr. Trump’s tweets made his job more difficult, Mr. Grenell appeared on Fox News to counter that view. “It makes my job so much easier,” Mr. Grenell said, offering the example of Mr. Trump’s pressure on NATO allies to spend more on defense.