KIEV, November 11 (RIA Novosti) - Ukrainian President Viktor Yushchenko believes Russia's Black Sea Fleet stationed on the Crimean Peninsula is leading to instability between the two countries' relations.

Russia's Black Sea Fleet uses a range of naval facilities in Ukraine's Crimea, including the base in Sevastopol, as part of a 1997 lease agreement valid until 2017. However, Yushchenko believes the Russian fleet should leave Ukraine before May 28, 2017.

"The existence of Russia's Black Sea Fleet [in Crimea] has seriously destabilized Ukrainian-Russian relations," Yushchenko was quoted by the UNIAN news agency as saying during a question and answer session on Wednesday.

Yushchenko said the country's Constitution forbids the deployment of military bases in Ukraine.

Yushchenko has led calls for Russia to prepare to withdraw its fleet from Ukraine's territory when the agreement expires in 2017, although Russia hopes to extend the lease.

A Russian-Ukrainian subcommittee on the Black Sea Fleet at the level of deputy foreign ministers holds regular meetings to discuss the implementation of the 1997 agreement.