Secretary of State John Kerry in Geneva on Thursday said that talks with Russia to secure Syrian President Bashar Assad’s chemical weapons stockpile are “not a game” and that the U.S. would press Moscow and Damascus to follow through on their promises.

“Expectations are high,” said Kerry at a joint press conference with Russian Foreign Minister Sergey Lavrov as the two began talks on an agreement that would turn over Syria's chemical weapons arsenal to international inspectors and avert a threatened U.S. strike. “They are high for the United States and for Russia to deliver.”

“This is not a game -- it has to be real,” Kerry added. “It has to be comprehensive, it has to be verifiable, credible, it has to be timely and implanted in a timely manner,” he said of a potential deal.

The secretary of state also warned that there “have to be consequences” if an agreement is not reached.

The Obama administration has charged Assad with using chemical weapons against civilians in his country's two-year brutal civil war.

President Obama has been pressing Congress to authorize a strike against Syria to punish Assad for crossing his "red line," but embraced the Russian proposal earlier this week after weak support among lawmakers and the public for military action.

Obama, though, warned in an address to the nation Tuesday that he would press for a strike if talks faltered or if Damascus failed to follow through.

The U.S.-Russian effort to broker a peaceful solution to the Syrian standoff has split lawmakers. Some express optimism that a U.S. strike can be avoided, while others doubt the talks will be fruitful and fear Russian President Vladimir Putin, a longtime ally of Syria, is buying time for Assad.

An op-ed from Putin in the New York Times Thursday also angered lawmakers, as the Russian leader mocked Obama's claims of American "exceptionalism" and warned the U.S. not to act against Syria without UN approval.

President Obama on Thursday at the White House said he was "hopeful" the Geneva talks would "yield a concrete result."

“I know that he is going to be working very hard over the next several days over the possibilities there,” Obama said of Kerry.

Disarmament experts though say the talks face many obstacles and that securing Assad's chemical arsenal in the midst of a civil war could be a long, costly process.

Kerry has been joined by technical experts to help negotiate the fine points of compliance. The White House though has declined to establish a timeline for talks.

Kerry acknowledged that there were broad disagreements between Moscow and Washington over Syria, including on the key question of who was responsible for a deadly Aug. 21 chemical attack. Russia disputes U.S. claims that Assad was responsible, blaming instead opposition groups.

But Kerry added there was “much that we agree on,” noting that an agreement to disarm Syria of chemical weapons would be a “historic moment” for nonproliferation efforts.

Assad in an interview on Thursday denied that the threat of U.S. action led him to decide to turn over his chemical arsenal. Syrian officials are also asking for 30 days to provide information to the UN about their chemical weapons program.