The United Nations Security Council will vote on Thursday on rival bids by the United States and Russia to extend an international inquiry to determine who was behind the chemical attacks in Syria in April, which killed more than 100 civilians. The mandate for a joint inquiry by the UN and the Organization for the Prohibition of Chemical Weapons into the April 4 sarin gas attack in Syria expires at midnight, Reuters reported.

The US was the first country to ask for a vote on its draft resolution, followed by Russia. To be adopted, a resolution needs nine votes in its favour and no vetoes by the US, China, Russia, France or Britain – the permanent members of the UN Security Council.

Russia, however, has vetoed nine UN resolutions on Syria since the conflict began in 2011, including a US bid on October 24 to renew the Joint Investigative Mechanism for inquiry into the use of chemical weapons in Syria. Russia has repeatedly questioned the findings of the team.

“The United States hopes the Security Council will stand united in the face of chemical weapons use against civilians and extend the work of this critical group,” the US mission to the UN said in a statement on Wednesday. “Not doing so would only give consent to such atrocities while tragically failing the Syrian people who have suffered from these despicable acts.”

British envoy to the UN Matthew Rycroft said if the inquiry ended, “the only victors would be people who want to use chemical weapons in Syria, which is the Assad regime and the Islamic State.” Reuters quoted an unidentified UN spokesperson as saying that Russia has refused to negotiate on the US draft, though Washington had amended it.