The UN Security Council voted unanimously to set up a panel to identify who is behind deadly chlorine gas attacks in Syria.
Russia, Syria's veto-wielding ally, endorsed the measure on Friday as did the rest of the 15-member council - a rare display of unity over how to address the conflict.
Under discussion for months, the US-drafted resolution sets up a team of experts tasked with identifying the perpetrators of the chemical weapons attacks and paves the way for possible sanctions to punish them.
The US ambassador to the United Nations, Samantha Power, called the probe panel a "necessary step" toward "eventual accountability."
The United States, Britain and France have repeatedly accused President Bashar al-Assad's forces of carrying out chlorine gas attacks with barrel bombs dropped from helicopters.
The three countries argue that only the Syrian regime has helicopters. Russia maintains there is no solid proof that Damascus is behind the attacks.
The investigative panel will be given "full access" to all locations in Syria and allowed to interview witnesses and collect materials, according to the resolution passed Friday (local time).
It mandates the panel to "identify to the greatest extent feasible individuals, entities, groups or governments who were perpetrators, organisers, sponsors or otherwise involved in the use of chemicals as weapons" in Syria.
UN Secretary-General Ban Ki-moon is tasked with assembling the team within 20 days, working with the Organization for the Prohibition of Chemical Weapons, which is based in The Hague.
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. It tops the UN's list of humanitarian crises.