The biggest hurdle for the U.S. strategy remains Russia, a major weapons supplier to Assad.
President Vladimir Putin's foreign affairs adviser, Yuri Ushakov, said Friday that Moscow doesn't believe the U.S. finding on chemical weapons.
"I wouldn't like to draw parallels with the famous dossier of Secretary of State Colin Powell, but the facts, the information presented by the U.S. didn't look convincing," he said. The comment indeed drew a parallel with Powell's speech to the U.N. asserting pre-war Iraq had weapons of mass destruction, a claim that proved false.
Ushakov also suggested that sending weapons to the opposition would diminish Moscow's interest in negotiations in Geneva.
"If the Americans make and fulfill a decision to provide a greater assistance to the rebels, to the opposition, it's not going to make the preparations for an international conference on Syria any easier," he said.
Obama's deputy national security adviser, Ben Rhodes, acknowledged the differences that remain between U.S. and Russia on the Syrian crisis. Despite their disagreement over chemical weapon use, the U.S. will continue to talk to the Russians about ways to achieve a political settlement in Syria, considered the best option by all .
"We have no illusions that that's going to be easy," Rhodes said, adding that Obama and Putin would meet next week.
Getting Western allies to increase support for the rebels won't necessarily be easy, either.
British Prime Minister David Cameron has said he there is credible evidence of "multiple attacks" using chemical weapons by Assad's fighters, but indicated that al-Qaida-linked elements in the opposition movement had also attempted to acquire chemical weapons for probable use in Syria. Still, he restated the government's position that no decision had been taken to arm moderate rebels opposed to Assad. The Obama administration says it has no evidence the opposition has used chemical weapons.