Trump: missiles will be coming to Syria

US President Donald Trump has taken to Twitter, exclaiming missiles 'will be coming' in response to a suspected chemical attack in Syria.

"Russia vows to shoot down any and all missiles fired at Syria," he wrote. "Get ready Russia, because they will be coming, nice and new and 'smart!' You shouldn't be partners with a Gas Killing Animal who kills his people and enjoys it."

At least 40 people died in the suspected poison gas attack.

Trump went on, tweeting, "relationship with Russia is worse now than it has ever been, and that includes the Cold War. There is no reason for this."

Russian lawmakers have said that an airstrike on Syria would be viewed as a war crime, triggering a direct military clash. Russia's ambassador to Lebanon said any missiles fired at Syria would be shot down and the launching sites would be targeted.