As UN weapons inspectors visit the site in an effort to establish who is to responsible for the attack, Hollande joined US and British leaders in blaming the Assad government and warning that a “red line” has been crossed.
“France is ready to punish those who took the despicable decision to gas innocent people, Hollande told an annual meeting of French ambassadors on Monday. “These past few days I had many meetings with our allies, American and European, as well as with our Arab partners, to consider all options.”
Support to the opposition Syrian National Coalition (SNC) is to be stepped up, he said, and later his office announced that he will meet SNC leader Ahmad al-Jarba on Thursday.
With the UN Security Council unlikely to back action in Syria, thanks to Russian and Chinese opposition, officials say a coalition of countries, including France, the US, the UK and Turkey, is likely to launch targeted strikes, possibly against ammunition depots or strategic infrastructure.
Under French law a one-off military intervention does not need parliamentary approval but junior minister Alain Vidalies, who is in charge of relations between the government and parliament, announced on Tuesday that a special meeting of both houses will take place on 4 September.
The leader of the right-wing opposition UMP, Jean-François Copé, - usually a strident critic of the president – found Hollande’s statement "correct in substance and in form" but warned against a long-term intervention, such as those in Iraq and Afghanistan.
Former prime minister François Fillon, Copé's rival for the UMP leadership, was more cautious, insisting that the UN must provide proof that the Syrian government is responsible before action is taken and calling for a last effort to persuade Moscow to put pressure on Assad.
But there are opponents on the right and on the left.
UMP lawmaker, Jacques Myard, warned against "encouraging an estemely composite opposition with jihadists waiting in the wings", while Florian Philippot of the far-right Front National recalled the false claims that Saddam Hussein had weapons of mass destruction in the run-up to the 2003 Iraq war.
"We're not in an American western," he said. "There are not always goodies and baddies."
"Don't try again to convince us that this time there will be a clean war," he said. "The only solution is to increase all kinds of pressure so that the belligerents sit down around a table."