David Cameron has defended the “strong stance” taken by the UK and US in response to the use of chemical weapons in Syria, claiming international pressure had led to a potential diplomatic breakthrough.
The Prime Minister said the proposal from Russia for international inspectors to seize and destroy chemical weapons in Syria would not have happened without the determination to stand up to Bashar al-Assad.
Barack Obama is conditionally endorsing the Russian offer, but insisted that US forces remained prepared to launch a strike if necessary.
Mr Cameron told MPs the development was a "vindication" of the "determination to stand up to chemical weapons use".
"We would not be in this position of pursuing new avenues of getting Syrian chemical weapons out of Syria and destroyed unless a strong stance had been taken," he said.
In response to Respect's George Galloway at Prime Minister's Questions, Mr Cameron added: "That is the right answer, not crawling up to dictators and telling them how wonderful they are."
Mr Galloway said that without Mr Cameron's defeat on the issue in the Commons "Britain and the United States would already be in the midst of what, it has turned out, would have been a wholly unnecessary war".
In a television address to the US, president Obama said he had asked congressional leaders to delay a vote on a resolution authorising limited military strikes, giving time to pursue the Russian plan and avoiding a potential humiliating defeat.
Speaking from the White House, Mr Obama admitted the prospect of a prolonged military campaign was unpopular with many and said: "I will not put American boots on the ground in Syria.
"I will not pursue an open-ended action like Iraq or Afghanistan. I will not pursue a prolonged air campaign like Libya or Kosovo.
"This will be a targeted strike to achieve a clear objective - deter the use of chemical weapons and degrading Assad's capabilities.
"A targeted strike can make Assad - or any other dictator - think twice about using chemical weapons."
President Obama said he had long resisted calls for military action in Syria because he did not believe force could solve the civil war.
But he said he changed his mind after the chemical weapons attack in Damascus on August 21.
Describing the images of death as "sickening", Mr Obama said: "On that terrible night, the world saw in gruesome detail the terrible nature of chemical weapons and why the overwhelming majority of humanity has declared them off-limits - a crime against humanity and a violation of the laws of war.
"On August 21, these basic rules were violated, along with our sense of common humanity."
Mr Obama said he was continuing discussions with Vladimir Putin, while dispatching secretary of state John Kerry to meet his Russian counterpart. He said the US would continue its "diplomatic path" to remove weapons without the use of force, with congress postponing a vote on authorising military action.
Mr Obama said he was also speaking to Mr Cameron and French leader Francois Hollande and would work with Russia and China to put forward a resolution at the United Nations Security Council requiring Assad to give up his chemical weapons.
The president said the United States could not be the "world's policeman", but added that the nation could save Syrian children from being gassed to death.
He said: "Sometimes resolutions and statements of condemnation are simply not enough.
"What kind of world will we live in if the United States of America sees a dictator brazenly violate international law with poison gas and we choose to look the other way?
"Our ideals and principles, as well as our national security, are at stake in Syria.
"It is beyond our means to right every wrong. But when, with modest effort and risk, we can stop children from being gassed to death and thereby make our own children safer over the long run, I believe we should act."