"We have defeated ISIS in Syria, my only reason for being there during the Trump presidency," President Donald Trump said on Wednesday.
Russia called for the withdrawal today, saying the US's presence is a roadblock to a peace settlement in Syria.
The decision upends assumptions about a longer-term U.S. military presence in Syria, which U.S. Defense Secretary Jim Mattis and other senior U.S. officials had advocated to help ensure Islamic State cannot reemerge.
Still, Trump has previously expressed a strong desire to bring troops home from Syria when possible.
The United States still has about 2,000 troops in Syria, many of them special operations forces working closely with an alliance of Kurdish and Arab militias known as the Syrian Democratic Forces, or SDF.
The partnership with the SDF over the past several years has led to the defeat of Islamic State in Syria but outraged NATO ally Turkey, which views Kurdish YPG forces in the alliance as an extension of a militant group fighting inside Turkey.
The pronouncement on U.S. troops comes as Ankara threatens a new offensive in Syria. To date, U.S. forces in Syria have been seen as a stabilizing factor in the country and have somewhat restrained Turkey's actions against the SDF.
A complete withdrawal of U.S. troops from Syria would still leave a sizeable U.S. military presence in the region, including about 5,200 troops across the border in Iraq.
Much of the U.S. campaign in Syria has been waged by warplanes flying out of Qatar and other locations in the Middle East.
Still, Mattis and U.S. State Department officials have long fretted about leaving Syria before a peace agreement can be reached to end that country's brutal civil war, which has killed hundreds of thousands of people and displaced around half of Syria’s pre-war population of about 22 million.
In April, Mattis said: "We do not want to simply pull out before the diplomats have won the peace. You win the fight — and then you win the peace."
Islamic State is also widely expected to revert to guerilla tactics once it no longer holds territory.
A U.S. withdrawal opens Trump up to criticism if Islamic State reemerged.
Trump has previously lambasted his predecessor, Barack Obama, for the withdrawal of U.S. forces from Iraq that preceded an unraveling of the Iraqi armed forces. Iraqi forces collapsed in the face of Islamic State's advance into the country in 2014.