US President Barack Obama announced on Monday that he has approved the deployment of an additional 250 troops to Syria to support local forces in the fight against Islamic State.
"They are not going to lead the fight on the ground but help in assisting local forces in pushing Islamic State back," Obama said in Hanover, Germany.
He said the political initiative for peace was also needed "to end the suffering in Syria."
The president called on US allies to contribute more military trainers and to boost economic support for Syria and Iraq.
The Pentagon said the troops would advise Syrian opposition fighters, establishing connections with those forces and improving US intelligence on what is happening on the ground.
Spokesman Peter Cook however declined to provide specifics about where the troops would be based and exactly how many would be on the ground at any one time.
The State Department claimed the development did not renege on pledges by Obama and other US officials not to send "boots on the ground" to Syria.
Spokesman John Kirby stressed the message had always been that the US would not send a conventional large-scale troop deployment to undertake combat operations.
A contingent of about 50 US special forces was sent to Syria late last year to assist Kurdish-led forces in their ground offensive against Islamic State in northern Syria.
The US has reportedly provided limited covert support to Syrian rebels. But Obama has consistently been sceptical about the merits of intervention in Syria's five-year-long civil war, despite calls from Turkey and Gulf allies for more support for rebels fighting Syrian President Bashar al-Assad and Islamic State.
Syria's civil war, which started in 2011 after al-Assad's forces launched a brutal crackdown against protests, has cost a quarter of a million lives and displaced half the country's population, according to UN estimates.