MPs have rejected possible UK military action against Syrian President Bashar al-Assad’s government to deter the use of chemical weapons.
David Cameron said he would respect the defeat of a government motion by 285-272, ruling out joining US-led strikes.
The US said it would “continue to consult” with the UK, “one of our closest allies and friends”.
Labour’s Ed Miliband said US-UK ties could not simply be about doing what the American president says he wants.
The prime minister’s call for a military response in Syria followed a suspected chemical weapons attack on the outskirts of the capital Damascus on 21 August, in which hundreds of people are reported to have died.
The US and UK say the Assad government was behind the attack – a claim denied by Damascus, which blames the rebels.
Assad said Syria would defend itself against any aggression.
The UK government’s motion was in support of military action in Syria if it was backed up by evidence from United Nations weapons inspectors, who are investigating the attack.
They are due to finish their work on Friday and give their preliminary findings to UN Secretary General Ban Ki-moon at the weekend.
After the vote Prime Minster David Cameron said it was clear Parliament did not want action and “the government will act accordingly”.
Chancellor George Osborne told Radio 4’s Today programme there would be “national soul searching about our role in the world”.
He added: “I hope this doesn’t become a moment when we turn our back on all of the world’s problems.”
Defence Secretary Philip Hammond told BBC’s Newsnight programme the Assad regime would “be a little bit less uncomfortable tonight”.
He blamed the 2003 Iraq war for “poisoning the well” of public opinion against British military interventions in the Middle East.
Mr Hammond said he and the prime minister were “disappointed” with the result, saying it would harm Britain’s “special relationship” with Washington.
But he said he did not expect Britain’s decision to “stop any action” by other countries.
Labour leader Ed Miliband said the result meant military action was “off the agenda”, and added that MPs had reacted against the prime minister’s “cavalier and reckless” leadership.
“I think today the House of Commons spoke for the British people who said they did not want a rush to war,” he said.
Mr Miliband said Britain’s relationship with the US “cannot simply be about doing what the American president says he wants you to do”.
Thirty Conservative and nine Liberal Democrat MPs voted against the government’s motion.
The defeat comes as a potential blow to the authority of Mr Cameron, who had already watered down a government motion proposing military action, in response to Labour’s demands for more evidence of President Assad’s guilt.
The BBC’s political editor Nick Robinson said the prime minister had now lost control of his own foreign and defence policy, and as a result he will cut a diminished figure on the international stage.
He added that some strong advocates of the transatlantic relationship were worried that America may now question the value and reliability of Britain as an ally.
During the debate, Labour had seen its own amendment – calling for “compelling” evidence that the regime was responsible for chemical attacks – rejected by MPs by 114 votes.
But, unexpectedly, MPs also rejected the government’s motion.
Labour’s shadow foreign secretary Douglas Alexander said the government defeat was down to the “fatally flawed” case put to MPs by Mr Cameron and Deputy Prime Minister Nick Clegg, claiming the pair’s credibility was now diminished.
‘The system works’
Shadow defence secretary Jim Murphy said so many of Mr Cameron’s own MPs had voted with Labour because they were now “unwilling to take him at his word”.
Conservative rebel Douglas Carswell said: “There is not now going to be British military involvement in Syria, but that is a good thing; the system works.”
In other developments:
The BBC witnessed the aftermath of an incendiary bomb attack on a school playground which left scores of children with napalm-like burns over their bodies
The US said it would act in its “best interests” in dealing with the Syria crisis, following the British rejection of military intervention
The Foreign Office advised against all but essential travel to Lebanon because of a “heightened risk of anti-Western sentiment” linked to the possibility of military action in Syria
In a statement, the White House said President Obama believed “that there are core interests at stake for the United States and that countries who violate international norms regarding chemical weapons need to be held accountable”.
Obama administration officials on Thursday told a group of US lawmakers in a conference call that it was “beyond a doubt that chemical weapons were used, and used intentionally by the Assad regime,” said Eliot Engel, the senior Democratic member on the House Foreign Affairs Committee.
US Defence Secretary Chuck Hagel said: “The British have been very strong in condemning the Syrian regime’s use of chemical weapons and that vote in the parliament doesn’t change that and that’s a very significant position for any nation to take publicly.
“We’ll continue to work with Britain and consult with Britain as we are with all our allies.”
Earlier on Thursday, the five permanent UN Security Council members – the US, UK, France, Russia and China – held a short meeting, but diplomats said their views remained “far apart”.
One diplomat told the BBC that there had been “no meeting of minds”, with Russia and China on one side, and the US, UK and France on the other.
Meanwhile, Mr Assad told a group of Yemeni MPs on Thursday that Syria would defend itself against any aggression, according to Syria’s Sana news agency.
“Syria, with its steadfast people and brave army, will continue eliminating terrorism, which is utilised by Israel and Western countries to serve their interests in fragmenting the region,” he said.
See on www.bbc.co.uk