President Donald Trump says US troops will not completely withdraw from Syria until Islamic State militants there have been defeated.
In a tweet last month, he said all 2000 US soldiers in Syria would be brought home immediately, but he has now told reporters he never intended US troops would leave overnight.
National security adviser John Bolton, who is in Israel for talks, has also indicated a more gradual withdrawal.
"We're going to be discussing the president's decision to withdraw but to do so in a way that makes sure that ISIS is defeated and is not able to revive itself and become a threat again," Mr Bolton said.
"And to make sure that our defence of Israel and our other friends in teh region is absolutely assured and to take care of those who have fought with us against ISIS and other terrorist groups."
Kurdish groups that fought alongside US troops against IS are concerned a speedy US withdrawal from Syria would expose them to attacks by Turkey, which regards them as terrorists.
President Donald Trump has faced strong criticism over the planned US pullout.
When he first announced the move on 19 December, he said "they're all coming back and they're coming back now". US officials later said American forces had been given 30 days to leave Syria.
In his announcement, Mr Trump had also declared the Islamic State group had been "defeated".
However, speaking on Sunday before leaving for his Camp David retreat, he told reporters: "We're going to be removing our troops. I never said we were doing it that quickly.
"We're pulling out of Syria... and we won't be finally pulled out until Isis [IS] is gone."
Last month's announcement shocked allies and US defence officials alike, with Defence Secretary Jim Mattis and senior aide Brett McGurk resigning soon after. On Saturday, Department of Defence chief of staff Kevin Sweeney became the third senior Pentagon official to announce his resignation since Mr Trump's announcement.
Meanwhile, the US's Kurdish allies in northeast Syria were left feeling exposed, as Turkey - which regards them as terrorists - appeared poised to move against them.
Mr Trump seemed to row back last week when he said troops were being pulled out "slowly" and that they would be fighting remaining IS militants at the same time.