Reports say US President Donald Trump has promised a “forceful” response to the alleged chemical attack in Syria, as Western leaders consider what action to take.
“We have a lot of options militarily,” he told reporters. He added that a response would be decided “shortly”.
Mr Trump said the US was getting some “good clarity” on who was responsible for the incident in Douma on Saturday.
Medical sources say dozens were killed in the alleged attack but exact numbers are impossible to verify.
Mr Trump also discussed the incident with French President Emmanuel Macron late on Monday, and both leaders expressed a desire for a “firm response”.
The AFP news agency quoted French government spokesman Benjamin Griveaux as saying on Tuesday that “if a red line had been crossed, there will be a response”, adding that intelligence shared by the two leaders “in theory confirms the use of chemical weapons”.
In February Mr Macron threatened to strike Syria if proof emerged of the use of chemical weapons.
UK Prime Minister Theresa May has said she “utterly condemns” the “barbaric” alleged chemical weapons attack and called for backers of President Bashar al-Assad to be held to account.
The condemnation from Western leaders follows a tense meeting at the UN Security Council in which the US and Russia traded harsh words over the incident.
Russian representative Vassily Nebenzia said the alleged attack was staged and warned that US military action in response could have “grave repercussions”.
US envoy Nikki Haley said Russia – a Syrian military backer – had the “blood of Syrian children” on its hands and branded President Assad a “monster”.
Ms Haley has called for a vote on Tuesday on a draft resolution to set up a new inquiry into the use of chemical weapons in Syria.
But Russia says it cannot support the proposal because it contains “unacceptable elements”.