BERLIN (AP) — German Foreign Minister Heiko Maas said Wednesday he will hold a video conference next week with his Russian, Ukrainian and French counterparts to try to secure progress in efforts to end the conflict in eastern Ukraine.

A summit of the four countries’ leaders in Paris in December brought an agreement to revive the peace process and for Kiev and Russia-backed separatists to exchange prisoners. But it failed to resolve crucial issues such as a timeline on local elections and control of the borders in the rebel-held region.

Maas said he has spoken with his counterparts in recent days. “We noted, and no one disputed this, that significant parts of the decisions from the summit in Paris have not yet been implemented,” he said.

“That’s why it is important to give a new impetus to the decisions and the implementation of the decisions,” he said. The foreign ministers agreed to hold a video conference next week, he said, without specifying a date.

Last week, Ukrainian forces and Russia-backed rebels exchanged 34 prisoners.

Germany and France brokered a 2015 peace agreement for eastern Ukraine that was signed in Minsk, and have since sought to shepherd its implementation. But it remains unclear when their leaders will hold another summit with Russia and Ukraine.