On Thursday, the OPCW rejected voted against the Russian and Iranian proposal on investigation of a suspected chemical weapons incident in Syria’s Idlib.
"Lavrov expressed regret over the fact that at the OPCW the US opposed Russia's initiative to send inspectors to Syria to verify allegations of sarin use in Khan Shaykhunon April 4 and of the presence of poisonous substances on the Syrian Sha'irat airbase."
Lavrov and Tillerson agreed to study a possibility of launching an unbiased investigation into the Idlib incident under the Organisation for the Prohibition of Chemical Weapons (OPCW) auspices, the Russian Foreign Ministry said.
On April 4, the National Coalition for Syrian Revolutionary and Opposition Forces claimed that 80 people were killed and 200 injured in a suspected chemical attack in Khan Sheikhoun, putting the blame on the Syrian government. Damascus vehemently rejected the accusations and said militants and their allies were responsible.
In response to the Khan Sheikhoun incident the United States launched 59 Tomahawk cruise missiles at the Syrian military airfield in Ash Sha’irat, located about 40 kilometers (25 miles) from the city of Homs. Russia described the attack as an aggression against a sovereign state.
In January 2016, the OPCW announced that all chemical weapons in Syria had been destroyed.