WASHINGTON — President Trump has instructed his military commanders to quickly wrap up the American military operation in Syria so that he can bring troops home within a few months, senior administration officials said Wednesday. He dropped his insistence on an immediate withdrawal, they said, after commanders told him they needed time to complete their mission.

The president’s decision to keep the 2,000 troops on the ground in Syria for the immediate future came in a meeting of the National Security Council in the White House Situation Room on Tuesday, hours after Trump had told a roomful of reporters that “it’s time’’ to bring US forces home from a conflict that has been a crucial battlefield in the fight against the Islamic State.

At the meeting, Trump’s top military advisers told him they had drawn up plans to pull troops out of Syria immediately. But they also presented a plan for the forces to stay longer to clean out the residual pockets of Islamic State fighters and to train local forces to stabilize the liberated territory so that the group could not regain a foothold.

“How long do you need to do that?’’ the frustrated president asked Defense Secretary Jim Mattis and the chairman of the Joint Chiefs of Staff, General Joseph F. Dunford, according to an official present for the exchange.

They responded it was difficult to predict a precise timetable but that it would not take years. As long as the operation lasted months rather than years, Trump replied, “I can support that.’’

After that, discussion in the Situation Room turned to issuing a statement to reassure Syrian Arab allies that the United States would not cut and run and would reinforce Trump’s message that Persian Gulf states needed to do more to contribute to the stabilization and reconstruction of liberated areas.

“The military mission to eradicate ISIS in Syria is coming to a rapid end, with ISIS being almost completely destroyed,’’ Sarah Huckabee Sanders, the White House press secretary, said in the statement issued Wednesday. “The United States and our partners remain committed to eliminating the small ISIS presence in Syria that our forces have not already eradicated.’’

It was the latest instance of the president making an unscripted remark with far-reaching implications that prompted a behind-the-scenes scramble by his advisers to translate blunt talk into a workable policy. White House and administration officials also spent Monday and Tuesday trying to translate a series of confusing presidential tweets and comments on immigration into a coherent strategy, including a new legislative push and the deployment of the National Guard to the southern border.

The statement on Syria was issued one day after Trump made plain his eagerness to pull US troops out, arguing that the United States had essentially already won the battle against the Islamic State and saying that “sometimes it’s time to come back home.’’

“I want to get out — I want to bring our troops back home,’’ Trump said on Tuesday during a news conference with leaders of the Baltic nations. “It’s time. We were very successful against ISIS.’’

The White House insisted Wednesday that the president had not walked back his position on bringing troops home from Syria, nor was he calling for a hasty withdrawal.

“As the president’s maintained since the beginning, he’s not going to put an arbitrary timeline,’’ Sanders said. “He is measuring it in actually winning the battle — not just putting some random number out there, but making sure we actually win, which we’ve been doing.’’