WASHINGTON—President Barack Obama is close to authorizing a mission led by the U.S. military to train moderate Syrian rebels to fight the regime of Bashar al-Assad and al Qaeda-linked groups, a move that would expand Washington's role in the conflict, U.S. officials said.
A new military training program, if implemented, would supplement a small train-and-equip program led by the Central Intelligence Agency which Mr. Obama authorized a year ago.
U.S. officials said the new military program would represent a significant expansion of Washington's public efforts. U.S. officials don't discuss the CIA's limited training program because it is covert.
In a commencement address at the United States Military Academy at West Point on Wednesday, Mr. Obama will signal backing for the new training effort by saying he intends to increase support to the armed Syrian opposition, including by providing them with training. Mr. Obama isn't expected to provide details about how, or where, that training would be accomplished.
"The president will make clear his intention to expand our support to the moderate Syrian operation and increase our support to Syria's neighbors, who are dealing with the terrorist threats emanating from the situation Assad has created in Syria," a senior administration official said.
The proposed military training mission has been the subject of a nearly yearlong Obama administration debate pitting top American diplomats seeking leverage to pressure Mr. Assad against Pentagon leaders wary of open-ended commitments that risk deepening U.S. involvement in another messy Middle Eastern conflict....
Syrian opposition leaders say the program would be a step in the right direction but voiced skepticism that training alone could turn the tide. Opposition leaders say the U.S. also needs to give moderate fighters access to more powerful weapons, including antiaircraft missile launchers, so they can take out Mr. Assad's helicopters and attack planes.
Defense officials said it also remains unclear which countries in the region would agree to host such a mission and what criteria would be used to screen rebels to prevent Islamists aligned with al Qaeda from taking part. "The devil's in the details," a senior U.S. military official said. "A lot of conditions have to be met."
The move toward deeper U.S. involvement reflects a growing realization within the White House that more needs to be done to build up the capabilities of a proxy force inside Syria capable of challenging al Qaeda. Washington increasingly fears al Qaeda's network of foreign fighters in Syria and Iraq will become capable of threatening U.S. allies in the region, including Jordan.
The move also comes in response to mounting pressure on the White House from Middle Eastern allies who say Mr. Obama's reluctance to support moderate fighters has allowed al Qaeda-linked groups to now dominate the opposition.
U.S. officials counter that Turkey and Gulf states fueled the al Qaeda threat by turning a blind eye to the influx of foreign fighters and by funneling their support to disparate groups on the battlefield, splintering the opposition.
Washington's Gulf allies were particularly critical of Mr. Obama's decision last year to call off planned airstrikes against Assad regime targets in exchange for a deal to remove his chemical arsenal. Nearly all of Mr. Assad's declared stockpile of chemical weapons has been removed from the country, and a senior U.S. diplomat said the rest should be shipped out soon.
The U.S. ambassador to the United Nations, Samantha Power, and Secretary of State John Kerry have been the leading advocates within the administration of creating the military-led training program. They have argued that more U.S. support is needed to weaken Mr. Assad and his allies, and to challenge al Qaeda.
Many Pentagon officers voiced skepticism of the proposed training mission. In recent private meetings, Defense Secretary Chuck Hagel has questioned the feasibility of vetting a sufficient number of rebels to make a difference, according to officials.....
The Western-backed Free Syrian Army has been fighting a two-front war, against Mr. Assad and his allies on one side, and against al Qaeda and its allies on the other, but commanders say they have received scant support from the U.S.