Last year he sent 50 special operations forces into the country
US President Barack Obama is planning to send up to 250 extra American troops to Syria to fight Islamic State, bringing the total US deployment on the ground to 300.
The plan was announced by US officials ahead of a meeting in Germany today attended by Mr Obama, German Chancellor Angela Merkel and British Prime Minister David Cameron.
French President Francois Hollande and Italian Prime Minister Matteo Renzi will also join the talks in Hanover, which will consider the war in Syria and other foreign policy issues.
The additional deployment aims to accelerate recent gains against IS and reflects renewed confidence in the ability of US-backed forces inside Syria and Iraq to claw back territory from the militants.
Mr Obama has resisted sending US troops into Syria, where a five-year civil war has killed more than 250,000 people.
Last year he sent 50 US special operations forces into Syria in what was described as a "counterterrorism" mission.
Commenting on the further deployment, one US official said: "He (Mr Obama) intends to put in more...forces to the tune of 250 in Syria".
A second official added: "The president has authorised a series of steps to increase support for our partners in the region, including Iraqi security forces as well as local Syrian forces who are taking the fight to ISIL".
The deployment is expected to be officially announced during remarks by the US President at the Hanover Messe fairgrounds later today.
Speaking at a news conference with Ms Merkel on Sunday, Mr Obama said he was "deeply concerned" by a recent surge in violence in Syria.
Airstrikes and shelling pounded the city of Aleppo for the third straight day on Sunday, killing two young siblings and at least 24 others.
The northern city has been bitterly contested between insurgents and government forces since 2012.
At least 10 people were killed by rebel shelling on government-held areas in the city, according to activists and Syria's state news agency SANA.
Mr Obama said it is difficult to see how a so-called safe zone would work in Syria without a large military presence.
"The issue surrounding a safe zone in Syrian territory is not a matter of an ideological objection on my part," he said.
"It's not a matter of me not wishing I could help and protect a whole bunch of people. It’s a very practical about how do you do it?".