The United States plans to send small arms, ammunition and potentially anti-tank weapons to Syria's rebels, two officials familiar with the matter told CNN on Friday.
President Barack Obama's administration has declined to provide details about increased military assistance for the rebels following its announcement Thursday that Syria crossed a "red line" with its use of chemical weapons.
Ben Rhodes, a U.S. deputy national security adviser, told reporters that Washington will "increase the size and scope of the assistance."
When pushed for more details, Rhodes said: "I can't give you a specific timeline or itemized list of what that assistance is."
The weapons will be provided by the CIA, the officials told CNN's chief White House correspondent Jessica Yellin. The officials spoke on condition of anonymity because of the sensitivity surrounding the issue.
The U.S. announcement set off a series of claims and counterclaims in Syria and world capitals over the conflict that has claimed more than 90,000 lives with no sign of progress toward a political solution.
Britain backed the U.S. change in position, but Syria and its allies in Russia quickly sought to cast its integrity into doubt.
The Syrian foreign ministry accused Washington of releasing "a statement full of lies regarding the use of chemical weapons in Syria," according to a statement released on state TV.
And a government statement carried by the state-run Syrian Arab News Agency accused the United States of using "flagrant tricks to come up with any possible means to justify the decision of President Barack Obama to arm the Syrian opposition."
An aide to Russian President Vladimir Putin labeled as "unconvincing" the U.S. evidence of chemical weapons use by Syria.
However, British Foreign Secretary William Hague backed the U.S. government's assessment and called for a coordinated response from the international community.
'Weapons and ammunition'
Obama has been criticized at home and abroad for not acting sooner to assist the Syrian opposition, and the declaration that the red line of chemical weapons use had been crossed raised expectations of U.S. arms heading to the rebels.
"What we need, really, is weapons and ammunition, and especially anti-tank and anti-aircraft missiles," Gen. Salim Idriss of the rebel Free Syrian Army told CNN's Christiane Amanpour on Friday.
Idriss said he has not been told what type of weapons the United States will provide to the rebel army.
Louay Almokdad, political and media coordinator of the rebel Free Syrian Army, told CNN that he expected the United States initially to send ammunition, rather than heavy arms.
What complicates any U.S. military support for the opposition is that many of the rebel fighters are militants with pro-al Qaeda sympathies, the same stripe of militants America has battled in Iraq and Afghanistan.
They include the al-Nusra Front, a rebel group that the United States says has links to al Qaeda.
The rebels promised U.S. and European officials that any military weaponry they get won't end up with extremists among the anti-government forces, Almokdad said.
The officials told CNN that beyond small arms and ammunition, anti-tank weapons were also under consideration. They did not spell out what was being given to rebels, but small arms can include such items as rocket-propelled grenades, small rockets, mortars and mines as well as guns.
Anti-aircraft weapons were considered less likely, and Rhodes made clear Friday that Obama has ruled out sending any U.S. troops to Syria.
"The one option that we've basically taken off the table is boots on the ground," Rhodes said, adding that Obama has made the final decision on the step that "dramatically increases assistance to" rebel forces.
Presidential aide Yuri Ushakov told reporters the United States had shown Russian officials data and information on Syria's use of chemical weapons, Russia's state-run news agency RIA Novosti reported Friday.
"What we saw does not look convincing to us," Ushakov was quoted as saying.