U.S. President Donald Trump warned Russian Federation on Wednesday of imminent military action in Syria, declaring that missiles "will be coming" and lambasting Moscow for standing by Syrian President Bashar al-Assad.
Although the official read-out of the meeting, attended by all but three of Mrs May's senior ministers, does not specifically mention military action, it will be seen as an endorsement for an intervention expected within days.
May spoke with President Trump on Thursday night about the worldwide response to Syria, and they "agreed that the Assad regime had established a pattern of unsafe behaviour in relation to the use of chemical weapons", according to the Downing Street.
Britain has moved a step closer to potential military action against Syrian President Bashar Assad after Theresa May won the backing of senior ministers for action to deter any further use of chemical weapons by the regime.
"The Prime Minister said it was a further example of the erosion of global law in relation to the use of chemical weapons, which was deeply concerning to us all".
"We hope that there will be no point of no return, that the USA and the allies will refrain from military action against sovereign states", he said.
The attack was first reported by Syrian rebel group Jaish al-Islam on Saturday.
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It has been observed in subsequent military deployments in Libya and Iraq and many British lawmakers and voters are deeply sceptical of deepening involvement in the Syrian civil war.
Formally, the prime minister has the right to go to war without approval from parliament, but a convention has been established in previous conflicts where MPs have a vote either before or shortly after military action begins.
Opposition Labour Party leader Jeremy Corbyn said parliament should be consulted before May approved military action.
Parliament voted down British military action against Assad's government in 2013, in an embarrassment for May's predecessor, David Cameron.
Following the meeting, May spoke to Donald Trump and the pair agreed that the United Kingdom and the USA would "keep working closely together on the worldwide response", according to a statement from Downing Street.
Conservative former London mayoral candidate Zac Goldsmith tweeted: "We need a clear response to the Syrian chemical outrage".
The war plans of British leaders have been complicated in recent years by the memory of Britain's 2003 decision to invade Iraq after asserting - wrongly, as it later turned out - that President Saddam Hussein possessed weapons of mass destruction. The United States, and the European Union put the blame for the incident on Damascus, which refuted the accusations.