The United States wants the UN Security Council to set up an investigation on the use of chemical weapons in Syria following reports of chlorine gas attacks, diplomats said Wednesday.
The investigation would be carried out by a team of experts appointed by UN Secretary-General Ban Ki-moon, and tasked with establishing who is to blame for the attacks.
"There is mounting evidence of repeated use of chlorine" in Syria, a Security Council diplomat said.
"There is a proposal for a mechanism which would allow relevant experts to have the right kind of access to answer the questions about attribution," said the diplomat.
The United States is taking the lead for the proposal that is set to be discussed at the Security Council on Thursday, according to AFP.
Western diplomats are in contact with Russia, Syria's ally, to discuss whether Moscow would be prepared to support a draft resolution setting up the UN investigation.
Britain, France and the United States have accused President Bashar al-Assad's forces of carrying out the chlorine attacks, using barrel bombs thrown from helicopters.
The three countries argue that only the Syrian regime has helicopters, but Russia maintains there is no solid proof that Damascus is behind the attacks.
The move by the United States follows a Security Council meeting last month during which Syrian doctors gave graphic first-hand evidence of chlorine attacks.
A video of the doctors treating children after a chlorine bomb attack on the village of Sarmin in Idlib province left many council members in tears.
"We are actively engaged in conversations with UN colleagues regarding the continued use of chlorine as a weapon in Syria," a US official said.
"The Security Council must address the need to determine who is responsible for using chlorine chemicals as weapons in Syria."
"Doing so is critical to getting justice for the Syrian people and accountability for those who have repeatedly used chemical weapons in Syria," he said.
The OPCW chemical watchdog in January concluded "with a high degree of confidence" that chlorine gas had been used in attacks on three villages in Syria last year.
At least 13 people died in the attacks that were carried out from April to August, according to the Organization for the Prohibition of Chemical Weapons.
Assad's regime and the rebels have accused each other of using chemical agents, including chlorine, in the four-year war that has killed more than 220,000 people.