Donald Trump criticised his Russian counterpart, Vladimir Putin, for backing the "truly evil" Syrian President Bashar al-Assad following a deadly chemical attack in the country's six-year war.

In an interview with Fox Business' Maria Bartiromo, the US president also ruled out a full-scale war in Syria after he ordered a missile strike last week in response to a gas attack.

Some 59 Tomahawk missiles pounded the Shayrat airbase near the city of Homs. US intelligence believes Assad used this facility to launch a deadly gas attack involving a nerve agent on the rebel-held town of Khan Sheikhoun on 4 April.

"We're not going into Syria," Trump declared in an interview that will air on Wednesday (12 April). Fox Business Network released excerpts of the interview on Tuesday (11 April).

When asked about further US involvement in war-ravaged nation, Trump said: "No."

He added: "But if I see them using gas and using things that – I mean even some of the worst tyrants in the world didn't use the kind of gases that they used. And some of the gases are unbelievably potent. So when I saw that, I said we have to do something."

The president went on to brand Assad an "animal" for his actions in the country and hit out at his staunch support for the Syrian regime.

"Putin is backing a person that's truly an evil person. And I think that's very bad for Russia," he said. "I think it's very bad for Russia. I think that's very bad for mankind. It's very bad for this world."

"When you drop gas or bombs or barrel bombs – they have these massive barrels with dynamite and they drop them right in the middle of a group of people ... And in all fairness, you see the same kids, no arms, no leg, no face. This is an animal."

The president also lashed out at the Obama administration for his inaction in Syria, despite repeatedly urging his predecessor against military action as a private citizen.

"What I did should have been done with the Obama administration long before I did it. And you would have had a much better – I think Syria would be a lot better off right now than it has been," Trump told Bartiromo.

The Trump administration has wavered on its diplomatic policy on Syria. Prior to the chemical attack, Washington's ambassador to the UN, Nikki Haley, had previously said the "priority is no longer to sit there and focus on getting Assad out."

However, two days after the US launched missile strikes on the Shayrat airbase, Haley said getting Assad out is one of many priorities that include toppling the Islamic State (Isis) and finding a political solution to end years of bloodshed.