The UN has adopted a resolution aimed at identifying those behind chemical weapons attacks in Syria.
UN chief Ban Ki-moon and the head of the Organisation for the Prohibition of Chemical Weapons (OPCW) will be asked to prepare a plan to set up an inquiry.
The vote came after the US and Russia agreed on the final text of the resolution.
A mission to eliminate Syria’s chemical arsenal was set up after a deadly attack outside Damascus in August 2013.
Late last year, the OPCW declared it had removed or destroyed all 1,180 tonnes of declared toxic agents and precursor chemicals.
After Friday’s vote, the US ambassador to the UN, Samantha Power, said it was a clear message that the perpetrators would not go unpunished.
“Today’s resolution has been adopted with the council’s unanimous support,” she said.
“This sends a clear and powerful message to all those involved in chemical weapons attacks in Syria. The joint investigative mechanism will identify you if you gas people.
“It bears repeating as well that we need to bring the same unity that we have shown today to urgently find a political solution to the Syrian crisis.”
The resolution calls for Mr Ban and the OPCW to recommend a team of investigators within 20 days.
The US has expressed concern that the militant group Islamic State (IS), which controls large parts of Syria and Iraq, could get hold of chemical weapons.