Russia has tried to deflect blame for a deadly chemical attack away from the Syrian government, the US has said.
Syria has denied it and Moscow has instead blamed rebel forces.
“Russia’s allegations fit with a pattern of deflecting blame from the (Syrian) regime and attempting to undermine the credibility of its opponents,” said an official.
The government of President Bashar al-Assad carried out the assault on 4 April in Idlib province to hit rebels in the area, the report said.
A chemical agent was flown by aircraft that departed from the Shayrat airfield, the document said.
But they refused to comment on whether Russia colluded with Syria on the attack or knew about it in advance, a point echoed later by the US secretary of defence.
His comments came just after US Secretary of State Rex Tillerson arrived in Russia to challenge the Kremlin over its support for Mr Assad.