UNITED NATIONS (Reuters) - Russia rejected on Tuesday a report by an international inquiry blaming the Syrian government for a deadly toxic gas attack, casting doubt on whether the U.N. Security Council can agree to extend the investigation s mandate before it expires next week. Russia vetoed an initial U.S. bid to renew the joint  inquiry by the U.N. and the Organization for the Prohibition of Chemical Weapons (OPCW) on Oct. 24, saying it wanted to wait for the release of the investigation s report two days later. It has since proposed its own rival draft resolution, which deputy Russian U.N. Ambassador Vladimir Safronkov said on Tuesday aimed to enhance the effectiveness of the inquiry and correct  errors and systemic problems.   Without a comprehensive change it will become a tool to settle accounts with the Syrian authorities,  Safronkov told the 15-member Security Council on Tuesday during a meeting on the report by the U.N./OPCW Joint Investigative Mechanism (JIM). The report found the Syrian government was responsible for an April 4 attack using the banned nerve agent sarin in the opposition-held town of Khan Sheikhoun, killing dozens of people. The Syrian government has denied using chemical weapons. The chemical weapons attack prompted a U.S. missile strike just days later against a Syrian air base.  Russia is trying to shoot the messenger to cover up for the crimes of the Syrian regime,  Deputy British U.N. Ambassador Jonathan Allen told the Security Council. U.S. Ambassador to the United Nations Nikki Haley said there could be no higher priority for the Security Council than renewing the JIM mandate. Diplomats said the United States had amended its draft resolution in a bid to win Russian support.  Anyone who prevents us from achieving this goal is aiding and abetting those who have been using chemical weapons,  Haley said.  They are helping to ensure, not just that more women and children will die, but that those women and children will die in one of the cruelest, most painful ways possible.  A resolution must get nine votes in favor and no vetoes by Russia, China, the United States, Britain and France to pass. Allen told reporters the Russian draft resolution  has very little if any support in the council and no realistic prospects of success.  The JIM had previously 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. 