MUNICH (AP) — German Chancellor Angela Merkel said Saturday that it's uncertain whether a flurry of diplomacy aimed at resolving the crisis in Ukraine will succeed.

Merkel insisted after returning from talks in Moscow the previous night that "this crisis cannot be solved by military means" and "substantial steps" are needed to "fill with life" a much-violated September peace deal.

Addressing the Munich Security Conference, Merkel said of the latest peace efforts that "it is uncertain whether they will be successful." However she said that she and French President Francois Hollande, who accompanied her to Kiev on Thursday and Moscow on Friday, believe it is "in any case worth making this attempt."

"We have not yet had sufficiently good experiences" with agreements that have been made being honored on the grounds, she said, but that the answer to that can't be not to seek agreements.

Merkel also said she is "very doubtful" about the wisdom of supplying weapons to Ukraine, underlining doubts in Europe about a move advocated by some in the U.S.

Merkel's speech was attended by Ukrainian President Petro Poroshenko and U.S. Vice President Joe Biden. She planned to hold a three-way meeting with both on the sidelines.

Russian Foreign Minister Sergey Lavrov and U.S. Secretary of State John Kerry are also attending the conference.

Merkel, Hollande and Poroshenko plan to confer on Sunday by telephone with Russian President Vladimir Putin.

Putin's spokesman, Dmitry Peskov, said after Friday's talks that efforts were moving forward.

"Work is currently underway on drafting the text of a possible joint document on the implementation of the Minsk agreement, which would include the proposals made by the president of Ukraine and President Putin," Peskov said.