French President Francois Hollande has called for the EU arms embargo on Syria to be lifted in order to aid anti-government forces.
"We are ready to support the rebels, so we are ready to go that far," he said.
He told reporters that France and the UK agreed on the issue but that other countries would have to be convinced.
Russia, which is not an EU member and is one of Syria's principal allies, has strongly opposed any arming of Syria's opposition.
Mr Hollande was speaking in Brussels on Thursday, ahead of a meeting of EU leaders.
Syria is not a formal agenda item for the summit, but a British official said Mr Hollande and UK Prime Minister David Cameron would raise the conflict with other leaders on Friday, the second anniversary of the start of the Syrian uprising.
A British official told the BBC there was a "perversity" about the embargo, as it meant the Syrian government receives arms but not the opposition.
On Wednesday, Mr Cameron hinted that the UK might arm the rebels if the EU ban remained in place.
However, Russia - Syria's main European ally - has stated its explicit opposition to arming the rebels.
Germany, Austria and Sweden are among the EU states believed to be reluctant to lift the embargo, the BBC's Chris Morris reports from Brussels.
"We think that a political transition should be the solution for Syria," Mr Hollande said.
But he added: "We cannot allow the massacre of a people by a regime which right now does not want a political transition."
"France's view is that arms are being delivered to Syria - but to the regime of Bashar [al-Assad], in particular by the Russians," he went on.
Mr Hollande said France's aim was not a "total war", but to increase the pressure on the government.
French officials said on Thursday that they would press for EU talks on the embargo to be brought forward, because of the situation's urgency.
Earlier, the French Foreign Minister Laurent Fabius said France and the UK would consider arming the rebels even if the ban remained in place.
The UK has indicated that it might veto a forthcoming vote, due in May, to extend the embargo.
Mr Cameron said on Wednesday that it was "not out of the question we may have to do things in our own way".
The UN's Under-Secretary General for Humanitarian Affairs, Valerie Amos, sounded a note of caution on the prospect of ending the arms embargo.
"Any more proliferation of arms and any more fighting is going to make our job more difficult," she told Reuters news agency in Turkey, where she was meeting officials to discuss the refugee crisis.
Many countries are concerned that pouring more arms into Syria could escalate the conflict.
Russian Foreign Minister Sergei Lavrov said in a tweet posted on Thursday: "Syrians are caught in a tragedy and humanitarian crisis. But solving the problem by arming the opposition is not an option here."
Syrian state media said that arming the rebels would be a "flagrant violation" of international law.
Also on Thursday, the Syrian Observatory for Human Rights, a UK-based activist group, reported fresh bombardments by government forces in several areas, including in the city of Homs, where a rebel offensive in recent weeks has prompted government reprisals.
Eight soldiers died in a rebel attack on a checkpoint near the citadel in the centre of Homs, the Observatory said.