US President Donald Trump has tweeted that Russia should “get ready” for missiles to be fired at its ally Syria, in response to an alleged chemical attack near Damascus on Saturday.

“Get ready Russia, because they will be coming, nice and new and ‘smart!'” Mr Trump said in his tweet.

Senior Russian figures have threatened to meet any US strikes with a response.

President Bashar al-Assad’s government denies mounting a chemical attack on the rebel-held town of Douma.

In one his tweets on Wednesday, Mr Trump called the Syrian leader a “gas killing animal”.

In another, he painted a dark picture of US-Russia relations but said it did not have to be that way.

The US, UK and France have agreed to work together and are believed to be preparing for a military strike in response to the alleged chemical attack at the weekend.

On Tuesday, Mr Trump cancelled his first official trip to Latin America so he could focus on Syria.

That decision suggests the US response may involve a larger military operation than a limited strike.

French President Emmanuel Macron said any strikes would “not target allies of the [Syrian] regime or attack anyone, but rather attack the regime’s chemical capabilities”. But The Times newspaper reports that the UK’s Prime Minister Theresa May has urged Mr Trump to provide more evidence of the suspected chemical attack.

A US Navy guided-missile destroyer, the USS Donald Cook, is in the Mediterranean Sea, and the European air traffic control agency, Eurocontrol, has warned airlines to take “due consideration” while in the eastern Mediterranean over the next few days because of the possible launch of missiles into Syria.