Who is behind the Syria gas attacks?

Full access to all locations in Syria

The UN Security Council is set to adopt on Friday a draft resolution that would set up a panel to identify who is behind deadly chlorine gas attacks in Syria that the West blames on the Damascus regime.
Russia, Syria's veto-wielding ally, is expected to endorse the measure during a vote at the 15-member council that will mark a rare display of unity over how to address the conflict, diplomats said.
Under discussion for months, the US-drafted resolution would set up a team of experts tasked with identifying the perpetrators of the chemical weapons attacks and pave the way for possible sanctions to punish them.
The panel would be given "full access" to all locations in Syria and allowed to interview witnesses and collect materials, according to the draft resolution.
The United States, Britain and France have repeatedly accused President Bashar al-Assad's forces of carrying out chlorine gas attacks with 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 resolution mandates the panel to "identify to the greatest extent feasible individuals, entities, groups or governments who were perpetrators, organizers, sponsors or otherwise involved in the use of chemicals as weapons" in Syria.
UN Secretary-General Ban Ki-moon would be tasked with assembling the team within 20 days, working with the Hague-based Organization for the Prohibition of Chemical Weapons (OPCW).
The panel would present its first findings to the council 90 days after it begins its work, which would be for a duration of one year.
Pressure has been mounting on the Security Council to take action in Syria, where the war, now in its fifth year, has claimed more than 240,000 lives and tops the UN's list of humanitarian crises.
- Russian shift -
Russian support for the chlorine attacks probe is seen by some western diplomats as a shift from Moscow, which has shielded the Assad regime at the United Nations.
"There is a change of tone," a Security Council diplomat said this week, but he cautioned: "I don't want to overstate it."
Diplomats are separately working on a council statement backing a new push for UN peace talks that could yield a plan for a transition that the West insists must lead to Assad's exit from power.
Discussions are inching forward on a new tougher UN measure on banning the use of barrel bombs, building on resolutions that have condemned the practice.
Syria agreed to a US-Russia plan to dismantle its chemical weapons network and join an international treaty banning their use following a 2013 sarin attack on a Damascus suburb that sparked a global outcry.
The United States threatened military action against Damascus over the attack, but held off following the chemical disarmament agreement.
A total of 1,300 metric tonnes of chemical stockpiles have been removed from Syria under the deal.
But rights groups and Syrian doctors have since come forward with accounts of dozens of chlorine gas attacks that have in particular targeted Idlib province.
US Secretary of State John Kerry said Thursday that he had reached agreement with Russian Foreign Minister Sergei Lavrov on setting up the panel of experts.
"What we are trying to do is to get beyond the mere finding of the fact that it may have been used, and actually find out who used it, and designate accountability for its use," Kerry said.
Questions remain however over whether the so-called joint investigative mechanism will be able to travel to sites and gain evidence of chlorine attacks that would allow it to assign blame.
Getting the panel up and running will require several steps, each of which must be approved by the Security Council, giving Russia the opportunity to stonewall the investigation, diplomats said.