US President Donald Trump has frozen more than $US200 million in funds for recovery efforts in Syria as his administration reassesses Washington's role in the long-drawn conflict there, the Wall Street Journal reported, citing officials.

Trump called for the freeze on Friday after reading a news report noting that Washington had recently committed an additional $US200 million to support early recovery efforts in Syria, the Journal reported.

The decision is in line with Trump's declaration on Thursday when he said that America would exit Syria, according to officials, the Journal reported.

An additional aid of $US200 million was pledged by departing Secretary of State Rex Tillerson in February in Kuwait at a meeting of the global coalition against Islamic State.

Trump is spending Easter weekend at his Palm Beach, Florida, estate. During a speech in Richfield, Ohio on Thursday, he revealed his desire to withdraw US forces from Syria and turn over security to regional countries.

He said that based on allied victories against Islamic State militants, "We'll be coming out of Syria, like, very soon".

"Let the other people take care of it now. Very soon, very soon, we're coming out," Trump said. "We're going to get back to our country, where we belong, where we want to be."

The administration officials, speaking to Reuters on condition of anonymity, said on Friday Trump's comment during the speech reflected internal deliberations with advisers in which he has wondered aloud why US forces should remain with the militants on their heels.

Trump has made clear that "once ISIS and its remnants are destroyed that the United States would be looking toward having countries in the region playing a larger role in ensuring security and leaving it at that", one official said.

Such a policy is nowhere near complete, however, the official added.

The second official said Trump's national security advisers have told him US forces should stay in small numbers for at least a couple of years to make sure gains against the militants are held and ensure Syria does not essentially become a permanent Iranian base.

Top national security aides discussed Syria in a White House meeting recently but have yet to settle on a strategy for US forces in Syria to recommend to Trump going forward, the official said.

"So far he has not given an order to just get out," the official said.

About 2000 US troops are deployed in Syria.

Four officials at the State and Defense Departments and the CIA said on Friday they were surprised by Trump's Syria remarks, which one senior intelligence official said "appeared to be completely off the cuff".

They added, speaking on the condition of anonymity, that Trump's comments also appear to be part of a pattern that includes questioning the US commitment to Article 5 of the NATO Charter and suggesting the Pentagon will pay for a border wall with Mexico, positions that many or most national security officials opposed.

Trump last year went through a similar wrenching debate over whether to withdraw US forces from Afghanistan, ultimately agreeing to keep them there but only after repeatedly raising questions of why they should stay.