Britain’s foreign minister, Boris Johnson, canceled plans Saturday to visit Moscow, just hours before he was due to depart London, as tensions escalated between the U.S. and Russia over Syria.

Russian leaders, who have dubbed as illegal the U.S. action to punish the government of President Bashar al-Assad for its use of chemical weapons, ramped up the war of words late Friday when the country’s prime minister, Dmitry Medvedev, warned America was “one step away from military clashes with Russia.”

In an apparent show of force, a Russian frigate armed with cruise missiles, reportedly was heading into the Mediterranean. According to Russian state media, the ship, the Admiral Grigorovich, will dock at Tartus on the Syrian coast.

Russia also has pledged to bolster Syria’s air defenses.

News of the cancelation of the British foreign minister’s trip was relayed first by Johnson himself, who tweeted: “I will now not travel to Moscow on Monday 10 April.” He said his priority was to hold talks with Western allies about Syria and Russia’s support for Assad.

British officials say that Johnson’s trip was called off after the British foreign minister consulted his American counterpart, U.S. Secretary of State Rex Tillerson, who himself is due to visit the Russian capital in a few days.

They said Johnson wants to spearhead efforts to help shape a “coalition of support” against Russian activity in Syria. In a statement later, Johnson said, “Developments in Syria have changed the situation fundamentally.”

A Russian Foreign Ministry spokeswoman described the cancelation as “absurd.”

Johnson was due to hold talks with his Russian counterpart, Sergei Lavrov, and the two diplomats were expected to hold a joint news conference.

“It seems that our Western colleagues live in their own kind of reality in which they first try to single-handedly make collective plans, then they single-handedly try to change them, coming up with absurd reasons,” said Russian Foreign Ministry spokeswoman Maria Zakharova in a statement.

“Unfortunately, stability, and consistency have long stopped being the hallmark of Western foreign policy,” she added.

As the diplomatic turmoil unfolded, activists Saturday claimed Syrian government warplanes had again struck Khan Sheikhoun, the rebel-held town targeted earlier in the week in an alleged chemical weapons attack by the Syrian regime.

The Syrian Observatory for Human Rights, the London-based pro-opposition watchdog that gathers information from activists on the ground, claimed a woman was killed and three people wounded after being machine-gunned by jets in an eastern neighborhood.

The warplanes carrying out Saturday’s alleged raid are believed to have flown from al-Shayrat, the airbase targeted Thursday by the U.S. in a punitive barrage of 59 Cruise missiles strike, the greatest show of America firepower in more than a decade. Tuesday’s chemical attack left scores dead, including children and women, according activists. U.S. officials so far have not commented on the claimed raid. In addition, there was no confirmation by other monitors.

There also was an unconfirmed report of a U.S.-led raid against the Islamic State in the countryside around Raqqa, the terror group’s de facto capital in Syria. The observatory quoted local activists as saying missiles struck the village of Hanida, to the west of the city.

 
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