Britain's government said on Monday it had no plans to hold another parliamentary vote on Syria air strikes after last week's defeat but might revisit the issue if circumstances changed "very significantly".

Prime Minister David Cameron lost a House of Commons ballot on Thursday on taking action to punish Syria for alleged chemical weapons use, and had appeared to rule out any further vote.

But after US President Barack Obama said he would ask Congress to authorise military action against Syrian President Bashar al-Assad's regime, there has been pressure on Cameron to take up the issue again.

Defence Secretary Philip Hammond told lawmakers that while the government believed in the need for a "robust response" to the use of chemical weapons it had no immediate plans for a second vote.

"We believe that parliament has spoken clearly on this issue and is unlikely to want to revisit it unless the circumstances change very significantly," Hammond said.

He also launched a blistering attack on the opposition Labour party, saying it was a "bit rich" to ask for a new timetable on a vote when Labour's refusal to support the government's proposal had led to Cameron's defeat.

Both Cameron's spokesman and Deputy Prime Minister Nick Clegg had earlier said there were no plans for another vote.

But they refused to rule one out completely.

"Parliament has spoken and that is why the government has absolutely no plans to go back to parliament," the Downing Street spokesman told reporters.

"The position we are in is that parliament has expressed its will and that is the basis on which we will proceed," he added.

Clegg, whose Liberal Democrats are in coalition with Cameron's Conservatives, said he could "not foresee any circumstances that we would go back to parliament on the same question, on the same issue."

"We're not going to keep asking the same question of parliament again and again," Clegg said.

The careful wording of the government's statements left room for supporters of military action against Syria to keep pressing for a new vote once US lawmakers have decided.

Former international development minister Andrew Mitchell, a member of Cameron's Conservative party, said nothing should be ruled out.

"It may be, after lengthy and careful consideration, (that) Congress affirms its support for the president's plans and, in the light of that, our parliament may want to consider this matter further," he told BBC radio.

The US Congress is to debate Obama's push to attack Syria next week when they return to work, its speaker said.

Obama cited the British vote when defending his decision to let US lawmakers decide.

The international community is also awaiting the result of tests carried out by UN chemical weapons inspectors in Syria.

Cameron suffered the most humiliating defeat of his three years in power when Conservative rebels joined Labour in voting against military action by 285 to 272.

Labour leader Ed Miliband had called for "compelling" evidence that Assad's regime had gassed its own people.

Cameron's spokesman said the prime minister would keep pressing for a political solution to the Syria conflict at the G20 meeting of world leaders in Russia later this week.

The parliamentary vote led to fears in Britain that the country's so-called "special relationship" with the United States was at risk, with France the only other country apparently ready to back US military action.

But Hammond insisted Monday that London's defence and security ties with Washington were "strong and resilient".