MOSCOW, December 21./TASS/. In a telephone conversation with German Chancellor Angela Merkel, Russian President Vladimir Putin explained the reasons for the withdrawal of the Russian officers from the Joint Center for Control and Coordination of issues related to the ceasefire and stabilization of the situation (JCCC), the Kremlin press service said on Thursday.

Putin said, in particular, that "the Ukrainian authorities had been for a long time complicating conditions for the stay of our military and performance of their duties through different restrictions and provocations". "There was no reaction to our repeated suggestions to settle the inadmissible situation at hand," he said.

During the conversation initiated by Germany, "the leaders of Russia and Germany agreed to continue discussing pending issues, whose settlement is necessary to restart a full-scale activity of the JCCC," the Kremlin press service said.

They agreed "that aides to the two countries’ leaders will additionally address the terms that would make the return of the Russian officers within that structure possible," the press service added.

Putin and Merkel spoke in favor of translating into action as soon as possible the initiative on a mutual exchange of prisoners by the sides in the Ukrainian conflict. They also backed a Christmas truce declared by the Contact Group.

German Cabinet spokesman Steffen Seibert said in a statement the two leaders "welcomed the truce, announced in the run-up to Christmas and confirmed yesterday by the trilateral Contact Group, and expressed hope that it transforms into a long-term ceasefire in the east of Ukraine."

"The federal chancellor and the Russian president stressed the importance of agreements on prisoner swap, which should take place as soon as possible, being an important step toward implementing the Minsk agreements," the statement reads.

According to the spokesman, the sides also stressed the importance of work of the Joint Center for Control and Coordination of the Ukrainian ceasefire.

"Merkel stressed that the Center’s ability to perform its duties needs to be preserved," Seibert said. "The sides agreed that certain issues should be solved, so that Russian officers could return to the JCCC.".

The Russian officers making part of the JCCC left Donbass on December 19.

The Russian Foreign Ministry explained earlier that "Kiev was adamantly opposed to any documents regulating the JCCC's work." "Attempts to tackle the issue at the bilateral level, at the Minsk Contact Group or in the Normandy format were not successful," the ministry said.

Moreover, Ukraine, in violation of the agreements reached by the Russian and Ukrainian presidents on the JCCC, deliberately created a strained moral and psychological atmosphere for the Russian military servicemen that formed part of it, caused difficulties for performing their professional duties. In particular, it restricted the Russian officers’ access to the line of engagement, inspections at the joint observation posts deployed to the areas controlled by Ukraine.

"It came to banning communication with the local population. There were cases of Ukrainian military servicemen’s disrespectful attitude to their Russian counterparts," the Russian Foreign Ministry noted.

Members of the Contact Group on resolving the situation in eastern Ukraine decided to set up a Joint Centre for Control and Coordination at a Minsk meeting held on October 2, 2014. The JCCC is expected to coordinate processes concerning the Donbass ceasefire and resolve issues aimed at stabilizing the situation in the region in compliance with the Minsk Agreements.