Sarkozy, who is running for re-election, has announced a crackdown on people who follow extremist Islamic messages on radical websites in the wake of a spate of killings by an Al-Qaeda-inspired gunman.

His aide, Henri Guaino, said the government would take measures to block the entry of Sheikh Yusuf al-Qaradawi if he seeks to take up the invitation from the Union of French Islamic Organizations (UOIF), a Muslim umbrella group.

"The French government does not want any extremist preachers entering its territory," Guaino, a special advisor and speech writer to Sarkozy, told French Radio J.

"This person does not require a visa because he holds a diplomatic passport, but measures could be taken to prohibit him from entering France," he said.

Qaradawi, who is based in Qatar, is one of the most widely respected Sunni Muslim clerics in the Arab world and a household name in the Middle East thanks to his regular appearances on the Qatar-based Al Jazeera news channel.

A former member of Egypt's Islamist Muslim Brotherhood, he is independent of the group today but remains close to it.

The UOIF, one of three Muslim federations in France, is also close to the Muslim Brotherhood.

The issue of Islam and immigration in France has come to the fore of the presidential election since a French man of Algerian origin, Mohamed Merah, killed three Jewish children, a rabbi and three soldiers before being shot dead himself by a police sniper on Thursday.