By Brian Love

PARIS (Reuters) - Ex-president Nicolas Sarkozy sought on Tuesday to broker a truce between the two men locked in a leadership dispute that could break up France's right-wing opposition party just months after it lost power.

Nine days after a disputed internal leadership election that plunged his UMP party into crisis, the two politicians fighting to become leader agreed to hold a new election, but only if the re-run was endorsed first in a referendum among UMP members.

Their announcement followed a face-to-face meeting organized by Sarkozy, who has been in political semi-retirement since he lost power in May but remains a figurehead for many conservatives who want him to run for the presidency in 2017.

"This may signal a way of bringing all this to an end," said Alain Juppe, an ex-prime minister who tried but failed to broker peace at the weekend between Francois Fillon and the more hardline Jean-Francois Cope.

Sarkozy himself made no public comment and may be reluctant to do so at a stage where success is far from certain.

However, Daviid Douillet, a former Olympic judo champion and sports minister said Cope and Fillon were under heavy pressure from Sarkozy. "He's exasperated," Douillet told reporters.

The scale of the row reflects the fact that the position of UMP leader is normally a springboard for the party's presidential nomination.

Cope, declared winner of the UMP's November 18 leadership vote in ballot results that were revised on Monday after accusations of fraud from both camps, said he would accept an election re-run if UMP cardholders endorsed such a move first.

Fillon, who raised the specter of a party break up by opting to create a splinter group within the UMP, said he would settle for a new election too, as long as it would be organized in a way would avoid renewed dispute over the outcome.

"I am fighting over principles. Nobody today is in fact leader of the UMP," said Fillon, who has threatened to go to court and wants an election re-run within three months, supervised by an independent body.

Nine days of sparring and cries of massive fraud by Cope and Fillon are undermining the credibility of a party that has its roots in the post-war Gaullist conservative movement and ruled for a decade until May.

The debacle, described by conservative daily Le Figaro this week as "live suicide", has provided welcome distraction for Socialist President Francois Hollande as he grapples with a sickly economy and dismal approval ratings.

Even Hollande's party has pleaded for an end to the row, though, saying a government needs a functional opposition.

The row over finding a successor to Sarkozy has exposed a deep rift between followers of Fillon, a popular and urbane former prime minister, and Cope, a disciple of Sarkozy with more hardline views on immigration and religion.

It was not immediately clear whether Cope and Fillon would manage to overcome personal enmity and a poisonous climate in coming days on the basis of the tentative solution that they announced after Tuesday's meeting with Sarkozy.

"We're talking. Contact is established," said Eric Ciotti, the man who led Francois Fillon's campaign for the leadership.

(Additional reporting by Catherine Bremer; Editing by Alison Williams)