President Barack Obama has said the credibility of the US, its Congress and the international community is on the line over their response to Syria’s alleged use of chemical weapons.
Speaking in Sweden, he said the world should stick to its own “red line” against the use of chemical weapons.
Mr Obama is trying to build support in the US for punitive military action against the Syrian government.
The US Congress will vote next week on whether to support his proposed action.
France – whose government has strongly backed the US plan for intervention – is holding an extraordinary debate in the National Assembly, though MPs will not vote on the matter.
Prime Minister Jean-Marc Ayrault stressed the need to take action together with France’s partners, saying: “Faced with barbarism, doing nothing is not an option.”
He said it was “France’s honour, France’s duty” to act and that President Francois Hollande was continuing efforts to bring together a coalition.
“What message would this send to other regimes, and I am thinking like you of Iran and North Korea? The message would be clear: You can continue,” he added.
Iran has rejected Western claims that it is seeking to build a nuclear weapon, while North Korea has a nuclear bomb but not yet the means to deliver it via a missile.
French Prime Minister Jean-Marc Ayrault: ”Bashar al-Assad has become a war criminal and has committed a crime against humanity”
The UK parliament voted last month against military intervention in Syria.
Russia remains firmly opposed, with President Vladimir Putin warning on Wednesday that any strike without UN approval would be “an aggression”.
But Mr Putin said Russia did not rule out supporting a UN Security Council resolution authorising force, if it was proved “beyond doubt” that the Syrian government had used chemical weapons.
He said it was “too early” to talk about what Russia would do if America took action without a UN resolution.
Meanwhile, Jordan’s Prime Minister Abdullah Ensour told the BBC that it would back intervention in neighbouring Syria if proof emerged that chemical weapons had been used.
But he said any strikes would have to be precise, and that Jordan itself would not be involved.
BBC