It was uncertain whether a military strike had been averted, or merely delayed.
French President Emmanuel Macron said he supports a "strong, joint response" to the attacks, and predicted a decision on whether to attack Syria's chemical facilities would be announced in the coming days.
British Prime Minister Theresa May's office said Britain, France and the United States have already decided that the perpetrators of the attack will be "held to account" for the suspected chemical attack against a rebel enclave in the Damascus suburb of Douma.
"The President has been clear we're working with our partners and allies and our national security team to look at all options," said White House press secretary Sarah Huckabee Sanders. "And as we've said, all options are on the table."
The United States has been building a circumstantial case, based largely on videos and photographs, that a chemical attack happened and it originated with Syrian government forces.
Syria and Russia, the main backer of Syrian President Bashar al-Assad, have insisted no attack happened and that only the opposition groups they call "terrorists" possess chemical weapons. They have called the reports a fabrication used to justify a military strike against Syria.
Russian and Syrian officials have each said they would ensure safe access for experts from the OPCW, an intergovernmental agency that won the Nobel Peace Prize in 2013. Many diplomats viewed the offer as a gambit to fend off a military strike, at least for the time being.
The OPCW said that it had asked the Syrian Government to make preparations for the team's deployment on a fact-finding mission. It gave no timeline but said the team is preparing to leave for Syria shortly.
At the UN Security Council, diplomats bemoaned their impotence as they met for the second time in as many days to discuss the suspected attack.
A US-drafted resolution demanded access to areas in Douma where the attack occurred, and would create a new investigative body "to look into chemical weapons attacks in Syria and determine who is responsible."
"At a certain point, you're either for an independent and impartial investigation, or you're not," said Nikki Haley, the US ambassador to the United Nations. "And now that the Douma attack has happened, this is not a decision that we can delay any longer."
The measure would have passed except for Russia's veto. Vassily Nebenzia spoke derisively of the United States, accusing it of stirring up a pretext for intervention.
"You tell us we covering up for someone," he said, glancing over at Haley after she said Russia would "stop at nothing" to shield the Assad Government.
"We are in Syria at the invitation of the legal government, to combat terrorism. Who are you covering up for? You cover up for terrorists."
A rival Russian-drafted resolution would have left the decision of culpability up to the Security Council - a step that would have allowed Russia or any of the five permanent members to kill it with a veto. Russia has repeatedly vetoed resolutions to protect the Assad Government.
The OPCW is not allowed by itself to determine responsibility for attacks. A joint task force the group took part in with the United Nations did have such a mandate, but Russia blocked its renewal last year after it blamed the Syrian Government for another attack.
The OPCW has worked in relative obscurity since it was founded in 1997 to oversee the implementation of the Chemical Weapons Convention, an arms control treaty that bans the development, production, possession and use of chemical weapons. Based in The Hague in the Netherlands, the group is independent but often collaborates with the United Nations.
