U.S. President Donald Trump and Britain’s Prime Minister Theresa May agree on the need to find an international response to deter the use of chemical weapons in Syria, the British prime minister’s office said on Thursday, cited by Reuters.

Trump and May spoke after May’s senior ministers gave her their backing to take unspecified action with the United States and France to tackle the use of chemical weapons by the government of Syria’s President Bashar al-Assad. 

“They agreed it was vital that the use of chemical weapons did not go unchallenged, and on the need to deter the further use of chemical weapons by the Assad regime,” May’s office said in a statement after the two leaders spoke. 

“They agreed to keep working closely together on the international response,” the statement added.