But the United States is "not interested in delaying tactics," White House press secretary Jay Carney told reporters.
"There is no question that the credible threat of U.S. military force brought us this diplomatic opening," Carney said. "Until two days ago, Syria did not even acknowledge that it possessed chemical weapons. We have seen more cooperation and helpful activity on this matter from the Russians in the last two days than we've seen in the last two years."
U.S. officials will review a potential U.N. agreement from Russia to secure Syria's chemical weapons stockpile, Secretary of State John Kerry said.
The draft U.N. resolution would come from Moscow a day after U.S. President Obama said in a nationally televised address he would hold off on military action and pursue Russia's proposal for international monitors to take over and destroy Syria's arsenal of chemical weapons.
"I don't have a timeline to give to you," Carney said. "What I can say is that it obviously will take some time. There are technical aspects involved in developing a plan for securing Syria's chemical weapons and verifying their location and putting them under international control. ... But we also are not interested in delaying tactics, and we believe it's very important to hold Assad accountable. What is, I think, very clarifying about this is, as the president made clear all along, the potential use of limited military strikes by the United States was in response to Assad's use of chemical weapons."
Carney said the process "needs to be credible. It needs to be verifiable."
The United States is "entering this with our eyes wide open, ... As the president has said, our military commanders, his military commanders have assured him that the military is ready and that waiting for a certain period of time will not negatively affect their ability to inflict the kind of damage that we envision on Assad's capabilities, if that were to become necessary.
"We, of course, remain skeptical of any commitments that Syria is making," Carney added. "The Assad regime is not shown itself particularly consistent in keeping its commitments. But it is absolutely the right thing to do to explore this possibility."
The United States says the Assad regime's latest use of sarin gas killed more than 1,400 people, including 426 children. More than 100,000 have died in the two-year-old Syrian civil war so far.