Prime Minister Theresa May, US President Donald Trump and French President Emmanuel Macron all shared phone conversations today discussing the “appalling cruelty” by Syrian dictator Bashar al-Assad, Daily Star reported.
Trump is expected to make a decision within the next 24 hours as to whether the US will launch military action against Syria.
US Navy destroyer USS Cole last year launched 59 cruise missiles at a Syrian air field in response to a chemical weapons attack.
Russia is backing Syria, denying the attack ever happened and warning the US to back down – saying an action will lead to "grave repercussions”.
Downing Street said the three leaders agree they would “work closely” to ensure “those responsible were held to account”.
The chemical assault on the rebel-held town of Douma as killed at least 45 people and injured hundreds of others.
Syrian military helicopters reportedly dropped barrel bombs packed with the toxins, which killed civilians and children.
Mrs May condemned the incident as a “barbaric” and said: " it's yet another example of the brutality and brazen disregard for their people that they show”.
US State Department officials said Downing Street and Washington have discussed "potential further steps the US and UK governments might take in coordination with other partners”.
Mrs May "agreed" that the "international community needed to respond to uphold the worldwide prohibition on the use of chemical weapons" in telephone conversations with Trump and Macron.
A Downing Street spokesman said: “They agreed that reports of a chemical weapons attack in Syria were utterly reprehensible and if confirmed, represented further evidence of the Assad regime's appalling cruelty against its own people and total disregard for its legal obligations not to use these weapons.
"They agreed that the international community needed to respond to uphold the worldwide prohibition on the use of chemical weapons.
"They agreed they would continue working closely together and with international partners to ensure that those responsible were held to account.”
Foreign Secretary Boris Johnson said in February that Britain should consider joining military action against Assad's regime if there is fresh "incontrovertible" evidence he has used chemical weapons against his own people.
Mr Johnson discussed the situation with acting US secretary of state John Sullivan twice on Monday.
Syrian opposition activists and rescuers said poison gas was used on the rebel-held town near the capital, an allegation strongly denied by the Assad government.
Families were reportedly found suffocated in their homes and shelters, with foam on their mouths.
Reports suggested more than 500 people, mostly women and children, were brought to medical centres with difficulty breathing, foaming at the mouth, and burning sensations in the eyes.
Russian ambassador to the UN Vassily Nebenzia said US attacks on Syria "could lead to grave repercussions" during heated exchanges at the UN Security Council.
US ambassador Nikki Haley accused Russia of having "the blood of Syrian children" on its hands after Mr Trump said that "nothing's off the table" in dealing with the alleged outrage.
Mr Nebenzia called for inspectors from the Organisation for the Prohibition of Chemical Weapons to fly to Syria on Tuesday to visit the site of the attack, which has left at least 40 people, including children, dead.
Tensions between the West and Russia over Syria come amid fears the world is plunging towards a new Cold War.