Senior White House officials have evidence to confirm the Assad regime used the deadly chemical agent sarin on its own people last week, and say Russia is helping the regime perpetuate faulty claims about the nature of the attack.

“The Syrian regime and its primary backer, Russia, have sought to confuse the world community about who is responsible for using chemical weapons against the Syrian people in this and earlier attacks,” a declassified four-page report distributed to reporters by the National Security Council finds.

In a briefing with reporters Tuesday, officials also accused Russia, a longtime ally of the Syrian government, of engaging in a cover-up about the nature of the attack.

“The cover up is the disinformation that has happened from the day of the attack,” one official said, pointing out the Russian claim that a Syrian regime airstrike on a terrorist ammunition depot near Khan Shaykhun caused the chemicals to leak.

Get Breaking News Delivered to Your Inbox

Earlier Tuesday, Russian President Vladimir Putin told reporters that the Assad regime used chemical weapons on its own people makes him recall the United States’ unproven claim that the Iraq had weapons of mass destruction.

“It reminds me of the events in 2003 when U.S. envoys to the Security Council were demonstrating what they said were chemical weapons found in Iraq,” he said. “That’s exactly what is happening now… We have already seen all of this.”

Rhetoric like this by Russia and Syria, the report states, aligns with how they expect Russia to act.

“Russia’s allegations fit with a pattern of deflecting blame from the regime and attempting to undermine the credibility of its opponents,” it says. “Moscow’s allegations typically have been timed to distract the international community from Syria’s ongoing use of chemical weapons...or to counter the findings from the Organization for the Prohibition of Chemical Weapons-United Nations Joint Investigating Mechanism.”

A senior U.S. official told the Associated Press Monday that Washington concluded Russia knew in advance of Syria’s chemical weapons attack. But officials in Tuesday’s briefing could not confirm whether Syrian President Bashar al-Assad ordered the chemical attack and said there is no consensus based on the information that they have that Russia worked in collusion with the regime. They did, however, note Russia and Syria’s long history of cooperation.

White House Press Secretary Sean Spicer reiterated Tuesday that there is little disagreement in the international community about Syria’s use of chemical weapons, and that Russia is in bad company about who aligns with them on the issue.

“Look at the countries that are standing with them — Iran, Syria, North Korea,” he said. “This is not a team you want to be on.”

In addition to contradicting Moscow’s claims point by point, the NSC report also lays out U.S. officials’ assertion that personnel “historically associated with Syria’s chemical weapons program” were positioned at Shayrat Airfield in late March, and were present on the day of the chemical attack.

“We believe certainly that there was an operational calculus that the regime, and perhaps its Russian advisers, went through in terms of its decision-making,” an official said, noting it is possible the Syrian government calculated their manpower was spread too thin in operations in other parts of the country.

“That’s why we saw, we believe, multiple attacks of this nature against locations that the regime probably determined were support areas for the opposition forces,” the official said.