The rivals in a bitter leadership row that split France's former ruling party, the rightwing UMP of Nicolas Sarkozy, agreed Monday to a new internal election after a contested first vote last month.
Jean-Francois Cope, the election's disputed victor, and his rival Francois Fillon, Sarkozy's former prime minister, said in a statement they had agreed to hold a new vote by October next year for the leadership of the Union for a Popular Movement.
"A new election for the presidency of the UMP will take place before the resumption of the regular parliamentary session of October 2013 at the latest," they said.
A first round of voting could be held on September 15, but close aides to Fillon have said the former prime minister may not run in next year's party election.
The deal aims to put an end to month-long infighting that has threatened to bring about the collapse of the UMP, the political heir to the movement founded by Charles de Gaulle after World War II.
In November, Fillon created his own parliament group, dubbed the Rally for the UMP (R-UMP), depriving the UMP of 68 of its 194 deputies.
The post of party leader is seen as the inside track to a candidacy for the next presidential election in 2017.
Previously, Cope had refused any fresh vote before the 2014 local elections.
Fillon's spokesman, lawmaker Jerome Chartier, said in an address to the National Assembly that the rivals had struck a "clear, unambiguous deal" that would identify the party's "indisputable" leader.
Both Fillon, 58, and Cope, 48, who will lead the party until the election, are fiscal conservatives advocating free-market policies and economic reforms, but Cope has carved out a niche on the right of the UMP with his tough-talking approach to immigration and Islam.
Sarkozy, who will be 58 next month, has no official post in the UMP after his defeat in the May presidential election to Socialist Francois Hollande.
But he is anxious to keep the UMP together in case he decides to make a comeback bid for the presidency in 2017.
Sources close to the former president have said he was infuriated by the deadlock after the November 18 election that was marred by allegations of irregularities and ballot-stuffing. In that close vote 175,000 party militants had taken part.
Sarkozy also threatened to announce they were both unfit to rule if they did not come to an agreement on when to hold a fresh vote, sources close to the former president and ex-UMP leader have said.
The former president, who wields influence over both Cope and Fillon, is currently seen as the only unifying figure who can salvage the party.
Cope and Fillon have suffered in opinion polls in the wake of the election upset.
A BVA poll published Monday showed that only 16 percent of respondents had a positive opinion of Cope, down 11 points in a month. His popularity plunged 29 percent with party supporters to 28 percent, making him the most unpopular politician on the French right.
Fillon lost six percentage points to 39 percent among the French public. Support from his party dropped 10 percent to 62 percent.
Cope will open the campaign for the party's top job as soon as January, according to an aide.