The president's national security adviser, John Bolton, told reporters on Sunday that any withdrawal would be on the condition that Turkey could assure the safety of Kurdish fighters in northeastern Syria, and that the remnants of ISIS in the region could be defeated.
"There are objectives that we want to accomplish that condition the withdrawal," he said, according to the AP. "The timetable flows from the policy decisions that we need to implement."
Speaking in Israel, ahead of traveling to Turkey for a meeting with its president, Tayyip Erdogan, Bolton said: "We don’t think the Turks ought to undertake military action that’s not fully coordinated with and agreed to by the United States, at a minimum, so they don’t endanger our troops but also so that they meet the president’s requirement that the Syrian opposition forces that have fought with us are not endangered."
The US has around 2,000 personnel in Syria. Concerns were raised that in the event of an immediate withdrawal, Kurdish militias who fought alongside the US against ISIS would be vulnerable from an attack from Turkey, which considers them terrorist insurgents.
Bolton was keen to stress, however, that there would be no arbitrary withdrawal point, "as President Obama did in the Afghan situation."
Officials traveling on the trip had also briefed reporters Saturday that some troops could remain in Syria.
Before Trump's surprise withdrawal announcement on Dec. 19, Bolton had said that US troops would stay in Syria as long as Iranian-backed forces were there. The next day, former defense secretary James Mattis announced his resignation.
Contrary to Trump's assertion that ISIS is defeated, there are some 30,000 fighters in Syria and Iraq, according to a US military estimate published last summer.
Recep Tayyip Erdoğan is Turkey's president. A previous version of this post used an incorrect title.