US President Donald Trump said on Tuesday he wanted to "get out" of Syria but offered no timetable, as his advisers warned of the hard work left to defeat Islamic State group and stabilize areas recaptured from the hardline militant group.
Trump told a news conference the United States would "not rest until ISIS is gone," using an acronym for the militant group. But he also suggested that victory was imminent.
The Pentagon and State Department have held that a longer term US effort would be needed to ensure that Islamic State group's defeat is a lasting one.
"It's time," Trump told reporters, when asked if he was inclined to withdraw US forces.
"We were very successful against (Islamic State group). We'll be successful against anybody militarily. But sometimes it's time to come back home, and we're thinking about that very seriously."
The United States is waging near-daily air strikes in Syria and has deployed about 2,000 troops on the ground, including US special operations forces whose advising has helped Kurdish militia and other US-backed fighters capture territory from Islamic State group.
US Army General Joseph Votel, who oversees US troops in the Middle East as the head of Central Command, estimated on Tuesday that more than 90 percent of the group's territory in Syria had been taken back from the militants since 2014.
Trump estimated the percentage of territory recaptured in Iraq and Syria at "almost 100 percent," a figure that US officials say is correct - it is about 98 percent - but does not highlight the work left in Syria.
The big hurdle, in the US military's view, is seizing Islamic State group-held territory around the Syrian town of Abu Kamal.
That effort that has been slowed as US-backed Kurdish fighters shift their focus away from Islamic State group toward a Turkish offensive against Kurdish allies elsewhere in Syria's complex, multi-pronged civil war, now in its eighth year.
Brett McGurk, the special US envoy for the global coalition against Islamic State group, speaking alongside Votel at an event in Washington on Tuesday, said the US fight against Islamic State group was not over.
"We are in Syria to fight ISIS. That is our mission and our mission isn't over and we are going to complete that mission," McGurk said.
Experts were divided about the significance of Trump's simultaneous musings about withdrawal and his assurance that the United States will not depart until Islamic State is defeated.
The militant group is widely expected to revert to guerilla tactics once the last remnants of its once self-styled "caliphate" are captured by US-backed forces.
Jon Alterman at the Center for Strategic and International Studies think-tank, said a precipitous US withdrawal would undermine US leverage in talks to end Syria's civil war.
"The principal consequence is the United States surrenders the little influence it has over the future of Syria," he said.
Experts warn an abrupt US withdrawal could benefit Russia and Iran, US rivals who could extend their influence in Syria.
Trump noted that US ally Saudi Arabia, Iran's arch-rival, was interested in his decision, adding: "Well, you know, you want us to stay, maybe you're going to have to pay."
Trump has previously lambasted his predecessor, Barack Obama, for his withdrawal from Iraq that preceded an unraveling of the Iraqi armed forces, which eventually collapsed in the face of Islamic State group's advance into the country in 2014.
It was unclear what Trump's vision of a post-war US role in Syria would look like. But his recent decision to freeze more than $200 million in funds for recovery efforts in Syria suggests resistance to a broad US ground effort.
McGurk acknowledged a review was underway to ensure US taxpayer dollars were well spent.
Votel said he saw a US military role in stabilization efforts in Syria.
"The hard part, I think, is in front of us, and that is stabilizing these areas, consolidating our gains, getting people back into their homes," Votel said, adding "there is a military role in this."