By Michelle Nichols

UNITED NATIONS (Reuters) – The United States said on Wednesday it would push the United Nations Security Council to renew within days an international inquiry into who is to blame for chemical weapons attacks in Syria, setting the stage for a likely showdown with Russia.

Russia has questioned the work and future of the joint inquiry by the U.N. and the Organization for the Prohibition of Chemical Weapons (OPCW), and said it would decide whether to support extending the mandate after investigators submit their next report.

The inquiry, known as the Joint Investigative Mechanism (JIM), is due to report by Oct. 26 on who was responsible for an April 4 attack on the opposition-held town of Khan Sheikhoun that killed dozens of people.

“We would like to see it renewed prior to the report coming out,” U.S. Ambassador to the U.N. Nikki Haley told reporters.

“The Russians have made it very clear that should the report blame the Syrians suddenly they won’t have faith in the JIM. If the report doesn’t blame the Syrians then they say that they will. We can’t work like that,” Haley said.

A separate OPCW fact-finding mission determined in June that the banned nerve agent sarin had been used in the Khan Sheikhoun attack, which prompted the United States to launch missiles on a Syrian air base.

Haley said she would circulate a draft resolution to the 15-member Security Council later on Wednesday to renew the mandate for the JIM, which is due to expire in mid-November. It was unanimously created by the council in 2015 and renewed in 2016.

A resolution must get nine votes in favor and not be vetoed by any of the council’s five permanent members – Russia, China, the United States, Britain and France – in order to pass.

The JIM has found that Syrian government forces were responsible for three chlorine gas attacks in 2014 and 2015 and that Islamic State militants used mustard gas.

Syria agreed to destroy its chemical weapons in 2013 under a deal brokered by Russia and the United States. The Syrian government has repeatedly denied using chemical weapons during a civil war that has lasted more than six years.

Mikhail Ulyanov, director of the Russian Foreign Ministry’s non-proliferation and arms control department, said on Friday there were “serious problems” with the work of the inquiry.

“In order to judge if it deserves an extension of the mandate, we need to see the report … and assess it,” Ulyanov told a briefing at the United Nations to present Moscow’s view on the “Syrian chemical dossier.”

(Reporting by Michelle Nichols; Editing by Paul Simao)