Theresa May has called China's President Xi Jinping to discuss Britain's involvement in missile strikes on Syria, Downing Street has said.
The prime minister argued the US-led action was a "proportionate, legal and responsible" response to the suspected chemical attack by the regime on the rebel-held city of Douma on April 7.
A No.10 read-out of the call said the two leaders agreed that use of chemical weapons "by anyone, anywhere, for any purposes was unacceptable".
China was one of just three members of the United Nations Security Council - along with Russia and Bolivia - to vote for a resolution condemning the strikes.
Beijing has previously joined Moscow in using its veto on the Security Council to block Western attempts to impose sanctions on the Syrian regime over its actions in the civil war.
In her call with Mr Xi, the prime minister suggested the international community should come together to establish an "independent mechanism" for attributing responsibility for incidents like Douma.
"The prime minister explained our strikes had been proportionate, legal and responsible, and aimed at alleviating humanitarian suffering by degrading the Syrian regime's chemical weapons capability and deterring their willingness to use them in the future," a No.10 spokesman said.
"The prime minister set out that Russia's blocking of diplomatic action underlined the importance of the international community working together to re-establish an independent mechanism that attributes responsibility to the perpetrators of attacks such as the one in Douma."
Mrs May also referred to the Salisbury nerve agent attack on former double agent Sergei Skripal and his daughter, which Britain blames on Russia.
"The prime minister noted that the use of a nerve agent against Yulia and Sergei Skripal in Salisbury was a grave attack on the sovereign territory of the UK, and the first use of nerve agents on European soil since the Second World War," the No.10 spokesman said.
"They agreed that the use of chemical weapons by anyone, anywhere, for any purposes was unacceptable."