PARIS (Reuters) - A top aide to French President Nicolas Sarkozy on Thursday visited Libyan leader Muammar Gaddafi, one of the fiercest critics of Sarkozy's Mediterranean Union project, just weeks before it is due to be launched.

France hopes leaders of all the countries that line the Mediterranean Sea will attend the body's launch summit in Paris on July 13, but there are doubts over whether Gaddafi and Algerian President Abdelaziz Bouteflika will come.

Any no-show would be an embarrassment for Paris.

Sarkozy's chief of staff, Claude Gueant, discussed the Mediterranean Union plan with Gaddafi, as well as nuclear cooperation and arms agreements signed with Tripoli in December, and France's tenure of the six-month rotating EU presidency, which begins on July 1, Sarkozy's office said.

"The meeting with Colonel Gaddafi focused on bilateral relations, regional and African issues as well as the project of a Union for the Mediterranean," Sarkozy's office said in a statement, using the project's official name.

Gaddafi poured scorn on the Mediterranean Union project earlier this month.

"This is taking us for fools," Gaddafi said. "We do not belong to Brussels. Our Arab League is located in Cairo and the African Union is located in Addis Ababa. If they want cooperation they have to go through Cairo and Addis Ababa."

France proposed a Union for the Mediterranean last year to boost ties with the European Union's southern neighbours and improve cooperation on trade, security and migration. In addition to other concerns, Arab states are worried that joining with Israel in the union would imply a normalisation of ties with the Jewish state.