Donald Trump has criticised Russia and suggested the US may take on a more forceful role in Syria after a devastating chemical attack killed dozens of civilians.

During a news conference he told reporters that the poison gas attack, which killed at least 72 people, was an "affront to humanity," which had changed his attitude on dealing with the conflict.

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Mr Trump said the atrocity - which he blamed on Syrian President Bashar al Assad - "crossed many, many lines," but he stopped short of saying how he would tackle the crisis.

In an interview with The New York Times, the President also said Moscow's role in the long-running civil war was "disappointing" - adding it was a "very sad day for Russia because they're aligned".


His remarks came after US Secretary of State Rex Tillerson said Russia needed to "think carefully about their continued support for the Assad regime", as he warned America was in "no doubt" that the embattled Syrian government was responsible for the attack.

Vice President Mike Pence, who was asked on Fox News whether it was time to renew calls for Mr Assad to be ousted from power, said: "Let me be clear, all options are on the table."

Chemical attack 'an affront to humanity'

Their comments come a matter of days after several senior Trump administration officials said they were no longer focused on removing Mr Assad from power.

Even though many western countries have blamed the Assad regime for the worst chemical attack seen in Syria for four years, Moscow has insisted that Syrian rebels were behind the attack in Idlib province.

Russian officials said they believed the poison gas contamination was the result of a leak from a rebel chemical weapons depot hit by government airstrikes - a theory described by a senior White House official as not credible.

Britain's ambassador to the United Nations, Matthew Rycroft, has also challenged Moscow to stop supporting the regime, and said: "What is your plan? What is your plan to stop these horrific senseless attacks? We had a plan and we had the support and you rejected it to protect Assad."

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Meanwhile, the US ambassador to the UN appeared to threaten possible unilateral action if the Security Council "fails in its duty to act collectively".

A draft resolution proposed by the UK, France and the US to "condemn in the strongest terms the use of chemical weapons" has been described by Moscow as "unacceptable", based on "fake" information and "anti-Syrian" - and Russia has threatened to veto.

Two US officials told the Associated Press that preliminary reports indicate the attack likely involved chlorine and traces of sarin. If nerve agent was used, this would suggest Syria has reneged on a deal to give up chemical weapons.

Footage from the attack in the town of Khan Sheikhoun showed people convulsing and foaming from the mouth, with medics using hoses to wash chemicals from victims' bodies - many of them children.

Image: Dozens of children were hurt in the suspected gas attack

President Trump now faces the same dilemma as his predecessor. In his first statement following Tuesday's attack, he had claimed Barack Obama's "weakness" on Syria while in office had enabled the Assad regime.

Openly challenging Moscow would mean Mr Trump risks deep involvement in a Middle East war by seeking to punish the Syrian government for using banned weapons, but compromising and accepting Mr Assad's continued grip on power could cause his administration to look weak.

Mr Trump's latest remarks have given some rebels cautious optimism that America's approach towards the civil war may be about to change - but others believe it is too early to tell whether any meaningful policy shift is forthcoming.

In the White House Rose Garden, Mr Trump had said: "When you kill innocent children, innocent babies - babies, little babies - with a chemical gas that is so lethal, people were shocked to hear what gas it was, that crosses many, many lines."

Fares al Bayoush, a Free Syrian Army commander, told the Reuters news agency: "(His) statement contains serious difference from the previous statements, and we expect positivity … from the American role."