The State Department said Monday it would take a "hard look" at a proposal for Syria to surrender its chemical weapons to international control to avoid a military strike, but voiced skepticism that Syria would carry out such a plan.

State Department spokeswoman Marie Harf said the U.S. would consider the proposal floated by the foreign ministers of Russia and Syria with "serious skepticism" because it might be a stalling tactic. She said Syria had consistently refused to destroy its chemical weapons in the past.

The proposal came after Secretary of State John Kerry said in London that Syrian President Bashar Assad could end the crisis by turning over all his chemical weapons. Harf said Kerry wasn't putting forth a formal proposal.

Kerry told reporters in London Assad could resolve the crisis surrounding the alleged use of chemical weapons by his forces by surrendering control of "every single bit" of his arsenal to the international community by the end of the week.

Hours later, Russian Foreign Minister Sergey Lavrov promised to push its ally Syria to place its chemical weapons under international control and then dismantle them quickly to avert U.S. strikes, and Syrian Foreign Minister Walid al-Moallem quickly embraced the proposal. That was followed by U.N. Secretary General Ban Ki-Moon also urged Syria to agree.

"Syria welcomes the Russian proposal out of concern for the lives of the Syrian people, the security of our country and because it believes in the wisdom of the Russian leadership that seeks to avert American aggression against our people," al-Moallem said during a visit to Moscow, where he met with Lavrov.

Even as the White House continued to build its case for action, with Obama taping six television network interviews late Monday and administration officials briefing more members of Congress as they returned from summer recess, administration officials sought to put the onus for the startling diplomatic maneuver on Russia, with administration spokesmen saying the White House would "take a hard look" at Russia's proposal.

U.S. officials in Washington initially said they were surprised by Kerry's comments, which came at a news conference with British Foreign Secretary William Hague and in response to a question about what, if anything, Assad could do to stop the U.S. from punishing it for the use of chemical weapons.

In a speech on Monday, Obama's national security adviser Susan Rice reiterated that the president had decided it is in U.S. interests to carry out limited strikes and still planned to make his case for a congressional authorization of military force to the nation in a Tuesday night television address.