The United States has accused Russia of trying to shield Syria's leader from blame for a deadly poison gas attack last week, as US Secretary of State Rex Tillerson brought a Western message to Moscow condemning its support for Syrian President Bashar al-Assad.
Senior White House officials, speaking on condition of anonymity, said Mr Assad's government carried out the 4 April sarin nerve gas attack on civilians in Syria's Idlib province, killing 87 people including many children, to put pressure on rebels who were making advances in the area.
Russia has defended Mr Assad, a staunch ally, against allegations his forces carried out the attack, saying there is no such evidence. Russia has blamed Syrian rebels.
"Russia is on an island when it comes to its support of Syria or its lack of, frankly, acknowledgment of what happened. The facts are on our side," White House spokesman Sean Spicer told reporters.
But at the same briefing Spicer drew criticism after he sought to underscore the ghastliness of the gas attack by saying, "You had someone as despicable as Hitler who didn't even sink to using chemical weapons."
Nazi Germany used gas chambers to kill millions of Jews during the Holocaust.
Mr Spicer later moved to clarify his remarks.
The White House officials said Russia has frequently offered multiple, conflicting accounts of Syrian government aggression, including the incident in the town of Khan Sheikhoun, to create confusion and sow doubt within the international community.
"Russia's allegations fit with a pattern of deflecting blame from the (Syrian) regime and attempting to undermine the credibility of its opponents," one White House official said.
The United States launched 59 cruise missiles at a Syrian airfield last Thursday to retaliate after the attack.
The attack has thrust the administration of President Donald Trump, which came to power in January calling for warmer ties with Russia, into confrontation with Moscow.
US intelligence indicates that the chemical agent in the attack was delivered by Syrian Su-22 aircraft that took off from the Shayrat airfield, according to a White House report given to reporters.
Mr Tillerson carried a message from world powers to Russia denouncing Russian support for the Syrian leader, as the Trump administration took on America's traditional mantle as leader of a unified West.
Mr Tillerson earlier met foreign ministers from the Group of Seven advanced economies and Middle Eastern allies in Italy.
They endorsed a joint call for Russia to abandon Mr Assad.
Mr Tillerson said Russia had failed in its role as sponsor of a 2013 deal under which Mr Assad promised to give up his chemical weapons arsenal.
Russia says the chemicals that killed civilians last week belonged to rebels, not to Mr Assad's government, and has accused the US of an illegal act of aggression against Syria on a false pretext.
Russian President Vladimir Putin said he believed the US planned to launch more missile strikes, and that rebels were planning to stage chemical weapons attacks to provoke them.
"We have information that a similar provocation is being prepared ... in other parts of Syria including in the southern Damascus suburbs where they are planning to again plant some substance and accuse the Syrian authorities of using" chemical weapons, Mr Putin said.
A senior Trump administration official called Mr Putin's remarks part of a Russian "disinformation campaign."
Mr Putin said Russia would urgently ask the United Nations chemical weapons watchdog to investigate last week's incident.
Western countries have dismissed Russian suggestions that the poison gas belonged to rebels as beyond credibility.
The US, Britain and France have proposed ar evised draft resolution to the 15-member UN Security Council that is similar to a text they circulated last week pushing Syria's government to cooperate with investigators.
