The move will significantly increase the U.S. presence in Syria and comes a week after Defense Secretary Ash Carter announced the deployment of a similar number of troops to Iraq, where Islamic State militants also control territory.Obama was expected to announce his decision Monday during a speech in Hannover, Germany, at the close of a weeklong trip, where IS was a focus of his meetings with world leaders in Saudi Arabia, Great Britain and Germany.
About 50 U.S. special operations forces are already operating in Syria. Most of the additional 250 personnel will also be special operations forces, largely Army Green Berets. The group will also include an unknown number of medical and logistical troops to provide them with support.
Senior U.S. officials have been touting the success of the forces in Syria, including their ability to generate critical intelligence that gives the U.S.-led coalition a better view of what is happening on the ground, including efforts to target insurgents.
In a sign of Obama's reluctance to use of force, Monday's announcement will cap a trip during which the president advocated diplomacy over military intervention.
Asked last week whether he planned to increase special operations forces in Syria, Obama did not answer directly. But he said he'd had discussions with an adviser about options should a fragile cease-fire break down.
"None of the options are good," he said in the Saudi capital of Riyadh. "It has been my view consistently that we have to get a political solution inside of Syria and that all the external actors involved have to be committed to that as well as the actors inside of Syria. ... The sooner we can end fighting and resolve this in a political fashion, the better."
Obama has said he remains opposed to large-scale U.S. military intervention in either Iraq or Syria. But he has incrementally deepened U.S. involvement in both countries.
The increase of U.S. troops in Syria has been discussed for weeks, including rumblings last week when Carter announced sending an additional 217 U.S. troops to Iraq, the first major increase in U.S. forces in Iraq in nearly a year. Eight Apache helicopters were also being sent to Iraq for the first time to help fight against the Islamic State group there.
Both moves were carried out to help Iraqi forces as they prepare to retake the key northern city of Mosul.
The deployment brought the total authorized troop total to just over 4,000.
Obama re-entered Iraq in June 2014 with an initial contingent of 170 soldiers serving Iraqi forces as advisers in June 2014, in response to the Islamic State group's seizure of much of the northern and western part of the country.
Obama's decision on Syria was first reported Sunday by The Wall Street Journal.
Associated Press writers Kathleen Hennessey in Hannover, Germany, and Lolita C. Baldor in Washington contributed to this report.