US Ambassador to the UN Nikki Haley holds photographs of victims during a Security Council meeting on Syria on April 5, 2017.

The UN Security Council will vote Wednesday on a draft resolution demanding that the Syrian government cooperate with an investigation of the suspected chemical attack last week in Idlib province, US diplomats said.

Britain, France and the United States put forward the measure, which was slightly revised from a previous text presented last week in response to the suspected sarin gas attack in the rebel-held town of Khan Sheikhoun.

The vote is scheduled for 3 pm (1900 GMT) and comes as US Secretary of State Rex Tillerson is in Moscow to ratchet up pressure on Russia to reconsider its support for Syrian President Bashar al-Assad. Russia is expected to use its veto to block the measure, diplomats said.

It would be the eighth time that Moscow has resorted to its veto power at the Security Council to block action against its ally Syria.

Draft resolution

The draft resolution expresses “horror” at the reported use of chemical weapons in Khan Sheikhun and condemns the alleged attack. The text expresses full support for investigators from the Organization for the Prohibition of Chemical Weapons (OPCW) and the joint UN-OPCW investigative panel tasked with determining who is responsible for such attacks.

The text calls on the Syrian government to provide flight plans, flight logs and other information on its military operations on April 4, hand over the names of commanders of any aircraft and provide access to all air bases to UN investigators.

The West has accused Assad’s forces of carrying out the attack that killed at least 87 civilians, including 31 children, on April 4.