Theresa May has agreed with Donald Trump and Emmanuel Macron that the international community “needed to respond” following reports of a suspected chemical attack in Syria.
The signs of international unity over the need for retaliation came as Russia vetoed a US resolution at the United Nations to create a new expert body to determine responsibility for the attacks.
Downing Street said the Prime Minister spoke to the US and French presidents on Tuesday, and they agreed to “continue working closely together” to ensure those responsible were “held to account”.
But how far May was willing to go in her support for Trump was questioned by contradictory briefings, with the Times reporting that “May resists calls to join US action against Syria” - a stark contrast to how other media had interpreted their conversations.
The United States is looking to the UK and France for support as it finalises its response to the assault on the rebel-held town of Douma.
President Trump and his French counterpart Emmanuel Macron had already agreed to co-ordinate a “strong, joint response” after talks by telephone.
A No 10 spokeswoman said: “They agreed that reports of a chemical weapons attack in Syria were utterly reprehensible and if confirmed, represented further evidence of the Assad regime’s appalling cruelty against its own people and total disregard for its legal obligations not to use these weapons.
“They agreed that the international community needed to respond to uphold the worldwide prohibition on the use of chemical weapons.
“They agreed they would continue working closely together and with international partners to ensure that those responsible were held to account.”
A White House statement said Trump and May “agreed not to allow the use of chemical weapons to continue”.
Meanwhile at the UN, UK ambassador Karen Pierce said it was a “sad day for the Security Council” and “for the people of Douma” after Russia vetoed the resolution to create a new expert body to determine responsibility for the Syria chemical weapons attacks.
Pierce told the Security Council: “By vetoing, Russia has crossed the line in the international order and worse, if possible, history is repeating itself one year on from Khan Shaykhun.”
She said Russia would “rather cross the WMD line than risk sanctions of its ally Syria”, and that instead the UN was being “asked to believe that the Russian version of this latest attack should be the one that the Security Council believes”.
Pierce added: “Russia’s credibility as a member of the Council is now in question. We will not stand idly by and watch Russia continue to undermine global norms which have ensured all our security, including Russia’s, for decades.”
It follows news of a suspected chemical attack by Syrian government forces in a brutal assault on the rebel-held town of Douma that left more than 40 people - including children - dead.
May is wary of the domestic political risks of promising military action, and has so far focused on the need to discover the facts about the attack and establish a common international response.
But she has also said that those responsible must be held to account and British diplomats have indicated that all options remain on the table.
Britain currently conducts air strikes in Syria from its military base in Cyprus, but only against targets linked to the Islamic State militant group.
In 2013, Parliament voted down British military action against President Bashar al-Assad’s government in a major embarrassment for May’s predecessor, David Cameron.
The vote effectively deterred the US administration of Barack Obama from similar action.
When asked whether Britain would join the United States if Washington decided on further military action in Syria, May on Tuesday declined to answer the question directly.
“We believe that those responsible should be held to account,” she told reporters in Cambridgeshire.
Underling the difficulties she faces, May must win MPs’ approval before backing military action in Syria, a motion with cross-party support demands.
Stewart McDonald, the SNP’s Westminster defence spokesman, is pressing for a fresh Parliamentary vote on any airstrikes against the Assad regime, and has won the backing of some Labour, Lib Dem and Green MPs.
The Prime Minister faces growing pressure from her own MPs to use executive powers to back military action without MPs’ approval, however.
Tom Tugendhat, chair of the Foreign Affairs Select Committee, said: “Striking Syria’s stockpiles of chemical weapons would degrade their ability to commit further war crimes and could be done together with allies. It would not require a vote in Parliament.”