Ukrainian President Petro Poroshenko on Tuesday held telephone conversations with German Chancellor Angela Merkel and U.S. Vice President Joseph Biden, the press service of the head of state has reported.

"The federal chancellor and the U.S. vice president expressed their condolences to the Ukrainian president in connection with the death of nine Ukrainian servicemen after a helicopter came under fire near Sloviansk," reads the statement.

Merkel expressed her admiration for the courage of the Ukrainian military and the people of Ukraine, "who, despite many losses, are seeking opportunities to resolve the conflict by peaceful means."

Poroshenko, in turn, condemned the incident, as well as attacks by terrorists that have been constantly made since the unilateral declaration of ceasefire by Ukraine.

Merkel assured Poroshenko of support in his efforts to implement a peace plan for eastern Ukraine.

"President Poroshenko, in turn, assured the German chancellor that the successful implementation of the peace plan requires concrete steps forward, among them, in particular, the blocking of the border, the cessation of attacks on Ukrainian checkpoints, the release of hostages, and the involvement of OSCE mission inspectors, including Russian representatives, in monitoring the situation at the checkpoints in the days remaining until the end of the declared ceasefire," the press service reported.

Poroshenko and Merkel also discussed preparations for a quadrilateral conference call with the heads of state in a format that was launched in Normandy.

Poroshenko and Biden agreed to coordinate efforts in the time remaining before the end of the ceasefire to ensure the full implementation of the peace plan.