WASHINGTON (AFP) - US President Barack Obama welcomed the deal reached on Saturday to strip Syria of chemical weapons but said much remains to be done and warned Damascus to comply with the accord.

In a statement, Mr Obama said that if the regime of Syria's President Bashar al-Assad does not live up to the deal Washington reached with Syria's ally Russia, "the United States remains prepared to act."

Mr Obama said the accord was made possible "in part" by what he called his credible threat to use force against Syria as punishment for its alleged use of chemical weapons against civilians last month.

The US says the attack killed more than 1,400 people while the regime and Russia have put the blame on the rebels. The accord marked a very swift change in the direction of the latest chapter of the Syria crisis.

Just two weeks ago Mr Obama seemed poised to order missile strikes against Syria, with the stated goal of degrading its ability to use chemical weapons again.

Then he surprised everyone by seeking Congressional approval, effectively delaying any military action for some time. Many US lawmakers opposed more military action for a country recovering from the traumas of Iraq and Afghanistan wars and polls showed voters wary of getting involved in Syria's civil war.

In the words of Mr Obama on Saturday, "we now have the opportunity to achieve our objectives through diplomacy." The new accord gives Syria a week to provide details of its chemical weapons stockpiles, and says Syria must give international inspectors unfettered access to them with the goal of removing them by the middle of next year.

The accord will be encapsulated in a UN resolution under Chapter VII of the UN charter. That chapter allows for use of force to ensure compliance, although Russia is certain to opposes this once diplomacy shifts to the UN.

"While we have made important progress, much more work remains to be done," Mr Obama said.

"The United States will continue working with Russia, the United Kingdom, France, the United Nations and others to ensure that this process is verifiable, and that there are consequences should the Assad regime not comply with the framework agreed today. And, if diplomacy fails, the United States remains prepared to act," the president added.

But two influential US lawmakers, John McCain and Lindsey Graham, said the agreement was a debacle.

"This agreement does nothing to resolve the real problem in Syria, which is the underlying conflict that has killed 110,000 people, driven millions from their homes, destabilised our friends and allies in the region, emboldened Iran and its terrorist proxies, and become a safe haven for thousands of Al-Qaeda affiliated extremists," the two Republican senators said in a jointly-released statement.

They added that they fear America's friends and foes alike will view the agreement "as an act of provocative weakness on America's part."

"We cannot imagine a worse signal to send to Iran as it continues its push for a nuclear weapon," said Mr Graham and Mr McCain, who was the Republicans' nominee for president in 2008.

"Assad will use the months and months afforded to him to delay and deceive the world using every trick in Saddam Hussein's playbook. It requires a willful suspension of disbelief to see this agreement as anything other than the start of a diplomatic blind alley, and the Obama Administration is being led into it by Bashar Assad and (Russian President) Vladimir Putin."

Earlier Saturday, in his weekly radio address, released as the accord in Geneva was emerging, Mr Obama spoke of Mr Assad in very harsh terms.

"A dictator must not be allowed to gas children in their beds with impunity. And we cannot risk poison gas becoming the new weapon of choice for tyrants and terrorists the world over," he said.

In his statement welcoming the accord Mr Obama said "the use of chemical weapons anywhere in the world is an affront to human dignity and a threat to the security of people everywhere." He said, "We have a duty to preserve a world free from the fear of chemical weapons for our children. Today marks an important step towards achieving this goal."