The relations between Russia and the US are on the verge of a total breakdown following the US decision to bomb Syria.
US President Donald Trump said the strike on al Shayrat airbase, near Homs, with some 60 Tomahawk missiles was “representing the world”. The base was allegedly used by Syrian forces to conduct the attack, which killed more than 70 people.
On Sunday the UK’s Defence Secretary, Sir Michael Fallon, demanded Russia rein in Mr Assad, claiming that Moscow is “responsible for every civilian death” in Khan Sheikhoun.
Sir Michael said the attack had happened “on their watch” and that Vladimir Putin must now live up to previous promises that Mr Assad’s chemical weapons had been destroyed.
Experts have dismissed Russia’s claim that a rebel chemical weapons facility caused the deaths.
Britain, the US and France accused Mr Assad’s regime of gassing civilians in the opposition-held town, but Damascus claimed it destroyed its toxic stockpiles following an international agreement struck in 2013.
The Russian defence ministry put out a competing version of events claiming legitimate Syrian air strikes against “terrorists” had struck a warehouse used to produce and store shells containing toxic gas, which were allegedly being sent to Iraq.
The joint command centre also said on Sunday the missile strike would not deter it from “liberating” Syria, and that the US military presence in the north of the country amounted to an illegal “occupation”.
Mr Putin and Iranian leader Hassan Rouhani have called for an objective investigation into the chemical attack.
US Secretary of State Rex Tillerson said on Sunday that Moscow had failed to carry out the 2013 agreement to secure and destroy chemical weapons in Syria.
“The failure related to the recent strike and the recent terrible chemical weapons attack in large measure is a failure on Russia’s part to achieve its commitment to the international community,” he said on ABC’s This Week.
Mr Tillerson is expected in Moscow in the coming days for talks with Russian officials.
He stopped short of accusing Russia of being directly involved in the planning or execution of the attack.
But he said the US expected Russia to take a tougher stance against Syria by rethinking its alliance with Mr Assad because “every time one of these horrific attacks occurs, it draws Russia closer into some level of responsibility.”