US holds Syria, Russia 'responsible' for chemical attack

US President Donald Trump holds Russia and Syria responsible for a suspected chemical attack that killed more than 40 people, the White House said Wednesday, refusing to rule out direct military engagement with Russia.

White House Press Secretary Sarah Sanders slapped aside Russian suggestions that Saturday's attack in Douma could have been faked and said Trump was still weighing military options in response.

"The intelligence provided certainly paints a different picture," she said of the Kremlin's theory. "The president holds Syria and Russia responsible for this chemical weapons attack"

Trump is believed to be considering standoff missile strikes against facilities related to the production and delivery of chlorine and sarin or sarin-like agents.

But many of Syria's most sensitive military facilities are protected by Russian missile defense systems or are located at bases where Russian, Iranian and Syrian personnel cohabit.

Sanders pointedly refused to rule out the possibility of direct military engagement with Russia -- not shying away from the specter of clashes between two nuclear superpowers.

"Once again, all options are on the table," she said.

Still, despite Trump's tweets early Wednesday which promised "nice and new and 'smart!'" missiles were headed for Syria, Sanders said no "final decisions have not been made on that front."

Secretary of Defense Jim Mattis as well as military personnel responsible for America's sea based Aegis missile defense system huddled at the White House on Wednesday to discuss options and game out the situation.

'Can't be allowed'

Since the attack in Douma on Saturday, Trump showed a visceral reaction to graphic images of pallid children struggling for breath and frantically being doused with water by first responders.

"As bad as the news is around the world, you just don't see those images," Trump said Monday, in one of a series of tweets and public remarks that appeared to telegraph the strikes.

"This is about humanity. We're talking about humanity. And it can't be allowed to happen," he said, surrounded by generals.

In April last year Trump ordered limited missile strikes on the Shayrat Airbase, in response to a similar chemical weapons attack on rebel-held Khan Sheikhun.

Official said at the time that he was moved by images brought to him by his daughter Ivanka and other White House officials.

But the pinpoint strike did not deter Assad. US officials, speaking on condition of anonymity, have since reported around 10 suspected chemical attacks of varying scale and certainty.

The same officials say Syria has continued to produce or procure chlorine, which is also has industrial and agricultural uses.

This latest chemical attack in Douma came days after Trump indicated a quick US withdrawal from Syria after defeating the Islamic State group.

Assad "likely calculated that the US would not respond if they escalated now," said Jennifer Cafarella of the Institute for the Study of War, "after President Donald Trump signaled his ultimate desire to withdraw from Syria."

Trump's predecessor Barack Obama had brokered a deal with Syria's ally Russia to remove chemical stockpiles from the country, a strategy which also failed.

Ned Price, a former CIA and National Security Council official during Obama's tenure told AFP the agreement led to the destruction of 1,300 tons of chemical weapons, but, he admitted, it was not enough.

"Even though the deal improved the situation considerably, we suspected the Syrians had failed to declare elements of their stockpile," he said.

"We worked assiduously through the final days of the administration to galvanize our allies and other international partners to help us address these omissions."