"I'll be continuing to talk with our allies and partners as I have done, speaking to President Macron this morning, and I'll be speaking to President Trump later today," UK Prime Minister Theresa May told reporters.
May said she would chair a meeting of Britain's National Security Council later on Tuesday.
"This attack that took place in Douma is a barbaric attack. Obviously, we are working urgently with our allies and partners to assess what has happened on the ground, if this is the responsibility of Assad's regime in Syria that is yet another example of brutality and brazen disregard for their people that they show," she said.
When asked whether Britain would support the US if Washington resolves to take further military action in Syria, May declined to answer but said: "We believe that those responsible should be held to account."
Western countries have been quick with the accusations and have blamed Damascus for the incident. US President Donald Trump has accused Russia and Iran of backing up Syrian President Bashar Assad in light of the reports of the alleged use of chemical weapons in the Arab Republic, adding that Damascus would pay a "big price."
Last week, the US Treasury Department added another 38 Russian entrepreneurs, senior officials and companies to its sanctions list in response to Russia's alleged "malign activity" worldwide.