Moscow immediately struck back, warning the Trump administration that “the gravest of consequences” would follow any retributive US military action.
The attack in Douma reportedly killed dozens and wounded hundreds more, according to independent Syria monitors, who have collected accounts and imagery from afar due to a lack of access to the site.
“Many dead, including women and children, in mindless CHEMICAL attack in Syria,” Trump wrote on Twitter. “Area of atrocity is in lockdown and encircled by Syrian Army, making it completely inaccessible to outside world. President Putin, Russia and Iran are responsible for backing Animal Assad.”
“Big price to pay,” Trump continued, nicknaming the embattled Syrian dictator and lashing out at his own predecessor, Barack Obama, for failing to act in Syria sooner.
"We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized," he said in remarks to the White House press corps in 2012. "That would change my calculus. That would change my equation."
But Russian media reported foreign ministry officials responding sternly: “Military intervention under false and fabricated pretexts in Syria, where Russian servicemen stay at the request of the legitimate government, is absolutely unacceptable and may trigger the gravest consequences,” the foreign ministry said.
Iranian media reported the country's ministry of foreign affairs condemned the use of chemical weapons but called the claims Assad's regime are behind the attack are "illogical and conspiratorial" and an "excuse for military action against Syria," Abas Aslani of Tasnim News Agency reported on Twitter.
Only days ago, Trump was talking not of holding Assad and his supporters accountable, but instead of pulling US forces out of Syria altogether— a move roundly opposed by his national security council and Mideast allies.
Trump remains committed to a pullout, his homeland security adviser, Tom Bossert, said in a Sunday morning show interview.
“The president’s got a point that’s been very clear,” Bossert said. “The pendulum has swung in the wrong direction for too long, and the United States of America has been taken advantage of in their responsibility to provide security for the entire world. It is time to move that pendulum back.”
But Bossert said that Trump still believes in the US’ responsibility to uphold international norms around the world, including those against the use of chemical arms. Asked if the president was considering a military response to the Douma event, he said, “I wouldn’t take anything off the table. These are horrible photos.”
The State Department “demanded” on Saturday night an “immediate response” from the international community upon confirmation that the Douma attack utilized chemical weapons.
Damascus and Moscow have denied that gas was used.
“We continue to closely follow disturbing reports regarding alleged chemical weapons attack targeting a hospital in Douma, #Syria,” wrote State Department spokeswoman Heather Nauert. “The Assad regime and its backers must be held accountable and any further attacks prevented immediately.”
US Vice President Mike Pence echoed Trump's message on Twitter and said the US is monitoring the situation.
Other permanent members of the UN Security Council also began weighing in on the attack, with UK foreign minister Boris Johnson stating those responsible had lost all moral integrity.
“Despite Russia’s promise in 2013 to ensure Syria would abandon all of its chemical weapons, international investigators mandated by the UN Security Council have found the Asad regime responsible for using poison gas in at least four separate attacks since 2014,” Johnson said in a statement. “These latest reports must urgently be investigated and the international community must respond. Investigators from the Organisation for the Prohibition of Chemical Weapons looking into reports of chemical weapons use in Syria have our full support. Russia must not yet again try to obstruct these investigations.”
The Douma strike comes on the heels of the first anniversary of another, large-scale chemical strike by Assad against civilians in Khan Shaykyun. That event— seen as an early test of a new US administration— prompted Trump’s first and only attack on Assad regime assets, and specifically targeted the air force facility that hosted the responsible strike force.
Reuters contributed to this report