Fillon was scheduled to have lunch with Sarkozy to discuss the UMP’s future after talks to resolve the party’s presidency collapsed late Sunday.
Party heavyweight, Alain Juppé withdrew from mediating the dispute between Fillon and party secretary general, Jean-François Copé after 45 minutes of talks.
Fillon has threatened to take the matter to the courts.
"Jean-Francois Copé holds sole responsibility for a failure that hurts our party and, furthermore, undermines the image of political activity," Fillon said in a statement.
"Anxious to break the deadlock into which Jean-Francois Copé's successive power grabs have plunged our party, I will refer the matters to the courts to restore the truth of the results and give a voice back to (party) activists," he said.
Fillon and Copé have accused each camp of fraud and ballot-rigging since last Sunday’s internal party vote ended with Copé announced the winner by just 98 votes.
The party’s electoral commission has since said that ballots cast in France’s overseas territories that were not counted would have reversed the outcome.
The dispute has rocked the UMP which is still recovering from its loss of the French presidency and parliament earlier this year.
Copé has held his ground following his win, saying he’s awaiting the decision of the electoral appeals commission and does not want to "mix the judicial process with the political process".
The commission was due to meet again on Monday.