PARIS — Echoing a warning by Britain, France threatened Thursday to deliver weapons to Syrian rebel groups on its own if the European Union refuses to lift an arms embargo on the embattled Middle Eastern nation.

The warning, from Foreign Minister Laurent Fabius, seemed designed to pressure the 27-nation European Union to change its policy, which bars arms deliveries to either side in the two-year-old civil war pitting President Bashar Assad against a broad-based rebel movement ranging from army deserters to Islamist extremists.