France said on Friday it was working with those close to Muammar Gaddafi to try to convince him to leave power as well as stepping up military pressure at the start of a second three-month NATO-led mission in Libya.

"He is more and more isolated," Foreign Minister Alain Juppe told Europe 1 radio. "There have been more defections around him and we have received messages from his close entourage which has understood that he must leave power."

"We will increase the military pressure as we have been doing for several days...but at the same time we are talking with everyone who can convince him to leave power," he said, speaking by telephone during a visit to Israel.

A NATO-led military alliance extended its mission to protect civilians in Libya for a further 90 days this week, after Gaddafi made it clear he would not step down in the face of a four-month-old uprising which has left thousands dead.

Libyan rebels and NATO have made Gaddafi's departure a condition for a ceasefire, but he emphatically told visiting South African President Jacob Zuma this week he would not leave Libya.

Libya's top oil official, National Oil Corp head Shokri Ghanem, became the latest figure to desert Gaddafi on Wednesday, two days after the defection of eight army officers including five generals and those in earlier weeks of senior diplomats and former ministers.

With the United Nations warning that his government was running out of food, the Libyan capital Tripoli this week saw the first big protest in months against Gaddafi's 41-year rule.

During his Middle East visit, Juppe made a last-ditch effort on Thursday to revive peace negotiations between Israelis and Palestinians before a likely showdown at the United Nations in September, proposing peace talks in Paris at the end of June or early July.

U.S.-brokered talks collapsed last year in a dispute over Jewish settlement building, and the Palestinians say that unless there is a breakthrough, they will seek U.N. recognition of statehood in September -- a step Israel strongly opposes.

Juppe said he believed there was a small chance the initiative would succeed and so far no-one had rejected the proposal.

"If there is a U.N. resolution in September that would not help to advance things. I fear that Israel would be more isolated and I don't think it would change things on the ground for the Palestinians themselves," he said.