France's President Nicolas Sarkozy warned that Iran's alleged attempts to build long-range missiles and nuclear weapons could lead unnamed countries to launch a pre-emptive attack, AFP reported.

"Its military nuclear and ballistic ambitions constitute a growing threat that may lead to a preventive attack against Iranian sites that would provoke a major crisis that France wants to avoid at all costs," he said.

Sarkozy did not say which country might launch such a strike, but it has been reported that Israel - perhaps with US support - has considered bombing Iranian nuclear sites if it believes Tehran is close to building a weapon.

The French leader placed the blame for the crisis on Iran, which insists it has no intention of building a nuclear weapon, and is merely enriching nuclear fuel for medical research and a domestic atomic energy program.

"Iran refuses to negotiate seriously," he told an annual meeting of French diplomats. "Iran is carrying out new provocations in response to the challenge from the international community for it to provide a credible response."