US President Donald Trump isn’t bluffing about retaliatory missile strikes on Syria, according to one Middle East expert.

Associate Professor Mehmet Ozalp, the director of the Centre for Islamic Studies at Charles Sturt University, told The New Daily that Mr  Trump’s warning of imminent military action over a suspected poison gas attack by Syria should be taken seriously.

“I think US strikes on Assad infrastructure are likely to come,” Associate Professor Ozlap said. “But whether that’s tokenistic [strikes] or something to bring down the Assad regime is hard to say.”

Mr Trump tweeted on Thursday morning (AEST) that missiles “will be coming” and slammed Moscow for standing by Syrian President Bashar al-Assad.

Mr Trump was reacting to an earlier warning from Russia that any US missiles fired at Syria over the deadly assault on a rebel enclave would be shot down and the launch sites targeted.

Russia vows to shoot down any and all missiles fired at Syria. 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!

— Donald J. Trump (@realDonaldTrump) April 11, 2018

His comments raised fears of direct conflict over Syria for the first time between the two world powers backing opposing sides in the country’s protracted civil war.

It prompted US-based Middle East expert Jonathan Schanzer to tell US media that the Syria conflict was beginning to look like World War III and was shaping up as “the ugliest Middle East War of the 21st century”.

But Associate Professor Ozlap said talk of “World War III” was a “bit of an exaggeration at this stage”.

“There’s a war happening – a war of words between Donald Trump and Vladimir Putin,” he said. “Merely a war of words. Certainly, if this escalation continues and the current trajectory continues then we might see a larger war, at least a regional war.

But I think these leaders would know the seriousness of this matter and would put the brakes on to prevent anything like that dangerous.”

Associate Professor Ozlap conceded Mr Trump’s language had become “reckless” which signalled a rethink on his plan announced last week to withdraw US troops from Syria. It also signalled a definite change in approach to the Obama administration.

“To what extent they [the US] are prepared to act has changed. Obama was very tentative to do anything in the Middle East, but Donald Trump is not like that.

“If he sees an economic or political benefit he will have no qualms about taking the steps that Obama was tentative about.”

The World Health Organisation said on Wednesday that 43 people had died in Saturday’s attack on Douma from “symptoms consistent with exposure to highly toxic chemicals”, and more than 500 in all had been treated.

After Mr Trump’s tweet, the Syrian Observatory for Human Rights – a British-based war monitor with a network of sources on the ground – reported that pro-government forces were emptying main airports and military air bases.

The Russian military said later it had observed movements of US naval forces in the Gulf.

Any US strike would probably involve the navy in waters within range of Syria, given the risk to aircraft from Russian and Syrian air defence systems.

A US Navy guided-missile destroyer, the USS Donald Cook, is in the Mediterranean.

The Syrian foreign ministry accused the United States, which has supported some rebel groups in Syria’s conflict, of using “fabrications and lies” as an excuse to hit its territory.

“We are not surprised by such a thoughtless escalation by a regime like the United States regime, which sponsored terrorism in Syria and still does,” the state news agency SANA cited an official source in the ministry as saying.

President Trump extended his uncharacteristic attack on Russia, saying the US’s relationship with Moscow was worse than ever, suggesting it needs American help with its economy.

Our relationship with Russia is worse now than it has ever been, and that includes the Cold War. There is no reason for this. Russia needs us to help with their economy, something that would be very easy to do, and we need all nations to work together. Stop the arms race?

— Donald J. Trump (@realDonaldTrump) April 11, 2018

-With AAP