The U.N. Security Council is due to vote on three draft resolutions on chemical weapons attacks in Syria on Tuesday, setting up a showdown between the United States and Russia over how to respond to a reported deadly gas attack last weekend.

The 15-member council is due to vote on a U.S.-drafted resolution that would establish a new inquiry to lay blame for chemical weapons attacks in Syria. A previous U.N.-mandated inquiry was shut down in November when Russia vetoed an extension of its mandate, slamming the investigation as flawed.

Russia also plans to put to a vote its own rival draft resolution on Tuesday to create an inquiry, which it first circulated in January.

Diplomats say both Russia and the United States are expected to vote against each other.

U.S. President Donald Trump on Monday warned of a quick, forceful response once responsibility for a suspected chemical weapons attack in the town of Douma on Saturday was established, thrusting Syria's conflict back to the forefront of international concern.

A resolution at the Security Council needs nine votes in favor and no vetoes by Russia, China, France, Britain or the United States to pass. A veto can only be cast if a draft wins at least nine votes.

"The U.S. draft that is being put to vote is not agreed," the Russian mission to the United Nations wrote in an email, seen by Reuters, to its council colleagues on Tuesday.

A veto of the U.S. draft by Russia - a close ally of Syrian President Bashar al-Assad - would be the 12th time Moscow has blocked action on Syria by the council during the country's seven-year-old conflict.

The key difference between the two drafts is that the U.S. one would mandate an inquiry to lay blame for chemical weapons attacks in Syria, while the Russian draft would require investigators to report to the Security Council, which would then attribute responsibility.

Russia also asked the council to vote on a second new draft resolution on Tuesday that would specifically support sending investigators from the global chemical weapons watchdog to the site of an alleged deadly attack last Saturday.

"US, UK and France can prove they want to establish truth by supporting this move," Russia's Deputy U.N. Ambassador Dmitry Polyanskiy posted on Twitter on Tuesday.

The Organisation for the Prohibition of Chemical Weapons said on Tuesday that inspectors would travel to the Syrian rebel-held town of Douma to investigate reports of the attack that killed as many as 60 people.

The Syrian government and Russia said there was no evidence that a gas attack had taken place and the claim was bogus.