US defence chief urges caution as Moscow warns against any move that could trigger conflict between US and Russia.

US defence chief James Mattis has urged caution in Washington, DC’s response against Syria, dialling back President Donald Trump‘s rhetoric about possible military action following reports a chemical attack in the besieged town of Douma last week.

In a public hearing on Thursday, Mattis told members of Congress that the US is “not going to engage in the civil war itself”, and it remains committed to the UN-backed negotiations in Geneva to end the war.

“We are trying to stop the murder of innocent people. On a strategic level – is how do we keep this from escalating out of control,” he said.

“Our strategy remains the same as a year ago: To drive this to a UN-brokered peace. At the same time, we keep our foot on the neck of ISIS until we suffocate it,” he said referring to the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group.

On Wednesday, Trump had threatened to retaliate against the Russian-backed Syrian regime, posting on social media that “nice, new and ‘smart'” missiles “will be coming”.

But he later wrote that “there is no reason” for the antagonism between Washington, DC and Moscow, adding that “we need all nations to work together”.

On Thursday, Trump added on Twitter that he “never said when an attack on Syria would take place” but it “could be very soon or not so soon at all!”

Russia concerned about ‘aggressive policies’

Russia had previously said that it would respond to any US missiles fired in Syria by shooting them down and targeting their launch sites.

Moscow’s UN ambassador Vassily Nebenzia said on Thursday that the “immediate priority is to avert the danger of war”.

He did not rule out the possibility of a US-Russia conflict, saying Moscow was very concerned with “the dangerous escalation” and “aggressive policies” that certain governments are making.

“We hope that there will be no point of return – that the US and their allies will refrain from military action against a sovereign state,” Nebenzia told reporters late on Thursday.

Russia has called for another emergency meeting of the UN Security Council on Friday.

The latest development in Washington comes as British media report that UK Prime Minister Theresa May‘s cabinet agreed “on the need to take action” in Syria.

At the same time, France’s President Emmanuel Macron was quoted as saying that he has “proof” that the Syrian government targeted civilians in Douma with chemical weapons last week.

‘We’re looking for evidence’

For Mattis’ part, he told members of Congress, “I cannot tell you that we have evidence” that the government of Bashar al-Assad was directly involved in the deadly attack, saying there are no US troops from the ground who could directly confirm the allegations.

“I believe that there was a chemical attack and we’re looking for the actual evidence,” he said, calling the deaths “absolutely inexcusable”.

At least 85 people, including many women and children, were killed in the Douma attack, according to a statement by rescue workers and medical staff.

A team of inspectors from the international chemical weapons watchdog is headed to Syria to begin an investigation into the suspected attack.

The incident would be the largest of its kind in Syria since April last year, when nerve agent sarin or a sarin-like substance was dropped onto the town of Khan Sheikhoun, killing at least 85 people.

Following that incident, the US launched a retaliatory cruise missile attack days later against a Syrian airbase from where it alleged the chemical weapons attack was launched.

Assad’s government and its ally Russia have called the allegations “fabrications”.