The UK will join the US and France in a push for a peaceful path forward to the Syrian crisis, proposing a new United Nations-backed ceasefire.
The three allies have produced a draft resolution that will be debated by the Security Council in New York, although it remains unclear when the vote will take place.
It comes as Nikki Haley, the US ambassador to the United Nations, said new sanctions would be imposed on Russian businesses that help the Assad regime make and deploy chemical weapons.
The proposed UN resolution includes a request for an independent investigation into the toxic gas attacks which killed more than forty civilians earlier this month and safe passage for aid convoys and medical evacuations.
A fact-finding team from the Organisation for the Prohibition of Chemical Weapons arrived in Damascus to "begin work" on Saturday, according to the organisation's Twitter feed.
The France-led initiative also demands that the Syrian government engage in peace talks "in good faith, constructively and without preconditions" and allows weapons inspectors into the country.
France's ambassador to the United Nations, Francois Delattre, said that Syria's chemical weapons program must be dismantled in a "verifiable and irreversible way."
"We must spare no effort to set up an international attribution mechanism, prevent impunity, and stop any repeat attempts by the Syrian regime."
Speaking to US media, Ms Haley defended the air strikes, warning that if action had not been taken, the United States could also become a target of chemical attacks.
"This (a chemical attack) very easily could happen in the United States if we're not smart, and if we're not conscious of what's happening," she said.
She also said that a new raft of Russian sanctions would be outlined Monday, by Steve Mnuchin, US treasury secretary.
"They will be going directly to any sort of companies that were dealing with equipment related to [Bashar] Assad and chemical weapons use," she told CBS News.
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Western diplomats are preparing for diplomatic efforts to convince Russia to vote for a ceasefire. Moscow has used its veto 12 times to block action targeting its Syrian ally.
Jean-Yves Le Drian, the French foreign minister, said renewed peace efforts should “begin with a ceasefire which is really respected this time.” A ceasefire in February failed.
President Emmanuel Macron was expected to strike a similar tone in a television interview on Sunday night.
Mr Macron is seeking to position himself as a broker between Russia and the Western powers. France has maintained regular contacts with Russia despite heightened tensions. Hours before the strikes, the French president discussed Syria in a phone call with Vladimir Putin, his Russian counterpart.
Mr Macron said he intended to go ahead with a planned state visit to Moscow at the end of next month. Next week he is to be hosted by Donald Trump on a state visit.
In Germany, the president warned against a “dangerous alienation” from Russia, as tensions grow between the country and the West.
Frank-Walter Steinmeier, a Social Democrat (SPD) politician, told the country's Bild am Sonntag newspaper that "we should not designate Russia in general, the country and its people, as an enemy".