US President Donald Trump vowed in a tweet that there would be a "big price to pay" for the reported chemical attack that killed dozens of people in a rebel-held enclave in Syria, leading international condemnation of the incident from democracies and authoritarian regimes alike.
As grisly images emerged of children's bodies in basements and bloodied survivors at hospitals in Eastern Ghouta, Trump made a rare direct criticism of Russian President Vladimir Putin.
In a series of tweets, Trump said Putin shared the blame for a "mindless CHEMICAL attack" through Russia's support of Syrian President Bashar al-Assad.
"President Putin, Russia and Iran are responsible for backing Animal Assad. Big price to pay," Trump tweeted. "Open area immediately for medical help and verification. Another humanitarian disaster for no reason whatsoever. SICK!"
His sentiments were shared around the world. British Foreign Secretary Boris Johnson called the attack an example of the Assad Government's brutality. The European Union issued a statement appealing to Assad's allies Russia and Iran to "use their influence to prevent any further attack and ensure the cessation of hostilities and de-escalation of violence." Turkey, which has been cooperating with Assad allies in talks for a political solution, called for international action to prevent what it called war crimes and crimes against humanity.
The calls for the White House to undertake some action in response, possibly military, came as the Administration's national security team is at a pivotal moment. John Bolton, a noted hawk on Russia and Iran, begins work as Trump's national security adviser tomorrow. On Friday, Mike Pompeo has a confirmation hearing scheduled before the Senate Foreign Relations Committee on his nomination to head the CIA.
And the Administration's position on Syria is evolving. Last week, the White House announced that the US military presence in Syria, where 2000 troops are stationed to prevent Islamic State militants from returning, is "coming to a rapid end."
Only last week, officials were commemorating the first anniversary of a sarin attack that killed more than 80 Syrians in the town of Khan Sheikhoun. That occurred shortly after the Administration said that it did not believe removing Assad from power was as big a priority as fighting Isis. The Syrian Government was deemed responsible in a joint inquiry by the United Nations and the Organisation for the Prohibition of Chemical Weapons.
The use of sarin at Khan Sheikhoun angered Trump and led him to reassess his attitude toward Syria and Assad.
"It crossed a lot of lines for me," he said. "When you kill innocent children, innocent babies, little babies, with a chemical gas that was so lethal," then it "crosses many lines, beyond a red line, many, many lines."
Three days after the attack, Trump ordered a missile strike on the Syrian airfield that had been used by planes that dropped the sarin.
Possible military action again seemed an option after the attack in Douma, amid calls for the international community to do something to punish the Syrian government.
Vice-President Mike Pence tweeted that US officials were monitoring the events, and condemned the assault. "The Assad regime & its backers MUST END their barbaric behavior," he added. "As POTUS said, big price to pay for those responsible!"
White House homeland security adviser Thomas Bossert said nothing should be taken "off the table."
"It's a quite serious problem," he said in an appearance on ABC News's This Week.
"We've seen the photos of that attack. This is one of those issues on which every nation, all peoples, have all agreed and have agreed since World War II this is an unacceptable practice."
Syria and its main backer, Russia, denied that chemical weapons had been used, calling such reports fabrications, while Iran deemed the alleged attack a "conspiracy."
"Such allegations and accusations by the Americans and certain Western countries signal a new conspiracy against the Syrian government and people, and a pretext for military action," Iran's Foreign Ministry said in a statement.
Russia's Foreign Ministry released a statement alleging information on the reported attack is a tactic being used to cover up for terrorists.
"The goal of these false conjectures, which are without basis, are designed to shield the terrorists and the implacable radical opposition, who reject a political settlement," the statement said. "It is necessary to warn, once again, that military intervention under such invented and fabricated pretexts in Syria, where Russian servicemen are based at the request of the legitimate government, is absolutely unacceptable and can lead to very serious consequences."
Syria also denounced as a lie the reports of chemical weapons.
"Jaish al-Islam terrorists are in a state of collapse and their media outlets are (making) chemical attack fabrications in an exposed and failed attempt to obstruct advances by the Syrian Arab army," the government-run news agency said about a rebel group that the government has been trying to oust from Douma.
Several prominent Republicans urged the president to act - and to reconsider his plan to withdraw US troops from Syria as quickly as possible.
House Speaker Paul Ryan, tweeted that responsible nations cannot tolerate chemical attacks. "The US must continue to lead an international effort to hold the Assad regime and Russia accountable for their actions."
Senator Susan Collins, (R), who sits on the Senate Intelligence Committee, called the alleged attack "absolutely horrific" and said that US officials should think about taking military action in response.
"Last time this happened, the President did a targeted attack to take out some of the facilities. That may be an option that we should consider now," Collins said on CNN.
Senator Lindsey Graham, (R), said that it is "no accident" that the Syrian regime seems to be once again using chemical weapons.
"They see us and our resolve breaking. They see our determination to stay in Syria waning ... but President Trump can reset the table here," Graham said. "If he doesn't follow through and live up to that tweet, he's going to look weak in the eyes of Russia and Iran. So this is the defining moment, Mr President. You need to follow through with that tweet; show a resolve that Obama never did to get this right."
Trump also blamed the Obama Administration for not ousting the Assad Government.
"If President Obama had crossed his stated Red Line In The Sand, the Syrian disaster would have ended long ago! Animal Assad would have been history!" he tweeted.