German Chancellor Angela Merkel said Saturday that she's still unsure of reaching a deal to calm the crisis in Ukraine, which France's president said could feature a broad demilitarized zone and greater autonomy for the separatist eastern region.

Merkel and French President Francois Hollande traveled to Kiev Thursday and Moscow Friday in a bid to defuse growing violence in Ukraine. The two leaders plan to discuss the proposals that have been thrashed out in a phone call Sunday with Russian President Vladimir Putin and Ukrainian President Petro Poroshenko.

Hollande, speaking on France 2 television, said the plan under negotiation would see a 31- to 44-mile demilitarized zone. He called for "rather strong" autonomy in the east.

The negotiators' aim is to draw up a possible joint document on implementing the much-violated September peace plan concluded in Minsk, Belarus. That agreement also featured a demilitarized zone, though the battle lines have since changed, and the government in Kiev has offered a measure of autonomy to the separatists.

"This conflict cannot be resolved by military means," Merkel said at the Munich Security Conference. "It is all the more important now to set out substantial steps that serve to fill with life the Minsk agreement."

Merkel said of the talks that "it is uncertain whether they will be successful, but it is from my point of view and that of the French president in any case worth making this attempt."

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The urgent diplomacy comes as Western anxiety over the conflict grows and sanctions bite ever harder on Russia's economy. More than 5,300 people have been killed since fighting began in April, according to a U.N. tally, and the bloodshed has markedly increased over the past two weeks.

The resurgent fighting has prompted the U.S. to consider giving lethal weapons to Ukraine, an option opposed by European nations.