The French prime minister, Édouard Philippe, has called for a “strong, united and resolute” reaction from the international community to the “alleged” chemical attack in Douma, a Syrian rebel-held town on the outskirts of Damascus.
“The use of these weapons is not neutral; it says things about the regime and our reaction to the use of these weapons will say things about who we are,” he said.
In phone calls, Theresa May, Donald Trump and Emmanuel Macron said those responsible should be “held to account”.
Mr Macron said any strikes would target Syrian government chemical facilities if it is found the attack was carried out by the government.
“First, we continue to exchange technical and strategic information with our allies to define our reaction, which will take place in the coming days. Second, we are strengthening our diplomatic action for the prohibition of chemical weapons. Third, we are taking action to help the civilian population to open humanitarian access with the UN and NGOs in the field,” he said.
The pressing question for France is what form any military action might take: what kind of strikes are possible and with what long-term aim?
Last week, US President Trump cancelled a planned trip to Latin America to focus on the issue. He has pledged a “forceful response”.
Last year, President Trump ordered a missile strike in retaliation for an alleged Sarin gas attack against a Syrian town. Two months ago, Defence secretary General Mattis said they still did not know who carried out last years attack.
The Organisation for the Prohibition of Chemical Weapons had said earlier that inspectors would travel to the town to investigate.