The British government has signalled that it was ready to back US military action against Syria, saying it was “highly likely” the Assad regime used chemical weapons on its own people and that such action could not go unchallenged.

British Prime Minister Theresa May’s senior ministers agreed on the need for action at a Cabinet meeting on Thursday, but Downing Street did not specify what measures the UK would take, reports CNN.

The ministers said there was a need to “deter the further use of chemical weapons by the Assad regime”, and alleviate the humanitarian situation, a Downing Street statement said.

According to the statement, May described the chemical attack on Douma in Eastern Ghouta as a “shocking and barbaric act which killed up to 75 people, including children, in the most appalling and inhumane way”.

Britain would work with the US and France to coordinate an international response, it added.

May spoke with President Trump on Thursday night about the international response to Syria, and they “agreed that the Assad regime had established a pattern of dangerous behaviour in relation to the use of chemical weapons”, according to the Downing Street.

Earlier on Thursday, Syrian President Bashar al-Assad warned the West against attacking Syria, saying accusations about the suspected chemical attack on Douma were “fabricated”.

French President Emmanuel Macron claimed that the country had “proof” the Assad regime used chemical weapons in Douma and would support any US action.

Trump has sent mixed messages on Washington’s readiness to act, reports CNN.

On Wednesday, Trump appeared to suggest airstrikes were imminent, warning Russia, Syria’s key ally, to “get ready” for military action.

But after being criticized for apparently telegraphing US intentions, Trump on Thursday attempted to blur the timing of any potential airstrikes on Syria.

Meanwhile, Russia has called for a UN Security Council meeting on Syria on Friday.

Earlier on Thursday, the Russian ambassador to the UN, Vassily Nebenzia, said that he believes any strike against Syria would violate the UN charter.