Russia's foreign ministry has dismissed the UK as having little real influence over world affairs after the British foreign secretary cancelled a visit to Moscow.

Boris Johnson decided not go to Russia amid growing pressure on President Vladimir Putin to cut his ties with Syria's Bashar al Assad in the wake of a suspected chemical attack that killed at least 87 people, including children.

Mr Johnson had been due in the Russian capital on Monday but will stay away as G7 foreign ministers draw up their coordinated response.

US secretary of state Rex Tillerson is then expected to deliver a message that the Kremlin faces international isolation if it stands by the regime in Damascus.

Russia said Mr Johnson's decision showed a lack of understanding of events in Syria and claimed there was little point in speaking to Britain anyway as it was "in the shadow" of its partners.

The cancellation "once again confirms doubts about the added value of dialogue with the British, who don't have their own position on the majority of current issues", the foreign ministry said in a statement.

"We don't believe we need dialogue with London more than (London) needs it (with us)."

It was later announced that Russia, Iran and Hezbollah would increase their support for the Syrian military after the US fired 59 cruise missiles at the airbase from which it believes the gas attack was launched.

Mr Putin and Iranian president Hassan Rouhani also called for an investigation into events in Idlib.

Mr Tillerson said on Sunday that Russia's inaction had allowed the chemical attack to take place.

"I think the real failure here has been Russia's failure to live up to its commitments under the chemical weapons agreements that were entered into in 2013," he said on ABC's This Week.

"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."

Russia has backed Syria for much of the six-year conflict, and has used its veto power in the UN Security Council on several occasions to prevent action being taken against the Damascus government.