Moscow on Thursday night warned against any US move that could trigger a conflict between the nuclear-armed rivals.

Russia's UN ambassador warned the priority in Syria was to avert US-led strikes that could lead to a confrontation between the world's two preeminent nuclear powers.

"The immediate priority is to avert the danger of war," said Ambassador Vassily Nebenzia following closed-door Security Council talks, refusing to exclude the possibility of US-Russian clashes.

Donald Trump, the US president, has slammed Russia for its partnership with "Gas Killing Animal" Bashar al-Assad, the Syrian president, spurring concerns that a US strike could lead to a conflagration with Russia, which has major military facilities at Tartus and Khmeimim and works cheek-by-jowl with Syria forces that could be targeted.

US officials have refused to rule out direct military engagement with Russia, with the White House saying "all options are on the table."

On Thursday, White House Press Secretary Sarah Sanders said Mr Trump would continue to assess intelligence and engage with allies.