MOSCOW — The leaders of France, Germany, Russia and Ukraine have vowed to go ahead with a peace plan for eastern Ukraine.

France, Germany and Russia have mediated talks between the Ukrainian government and Russia-backed rebels who have been fighting since April 2014 in a conflict that has killed more than 10,000 people.

Ukrainian President Petro Poroshenko’s office said that French President Emmanuel Macron, German Chancellor Angela Merkel and Russian President Vladimir Putin held a phone call Monday and vowed to help implement the peace deal they had brokered.

The separatists last week proclaimed a new state that aspires to include not only the areas in eastern Ukraine that they now control but territory beyond that. Poroshenko’s office said both Macron and Merkel vehemently rejected the idea of the rebel state.