In order to exchange Ukrainian pilot and MP Nadia Savchenko for the officers of the Main Intelligence Directorate (GRU) of the General Staff of the Russian Armed Forces, Yevgeny Yerofeyev and Alexander Alexandrov, the Russian servicemen should be sentenced first, a diplomatic source told Interfax-Ukraine.

"Verdict for the Russian intelligence officers is needed in order to free Savchenko," he told the agency adding that Moscow was going to exchange the Ukrainian pilot for Yerofeyev and Alexandrov.

According to him, lawyers the Russian servicemen "are in constant contact with the FSB (Russian Federal Security Service) and therefore their trial is being deliberately delayed." "I want to note that President Putin has previously promised Poroshenko and Merkel to swap Savchenko for the GRU officers," he said.

According to the source, Kyiv is working on the speedy return of the Ukrainian prisoner home.