Moscow violated the Treaty on Friendship, Cooperation and Partnership between Ukraine and Russia by occupying Crimea and part of Donbas, but its denunciation will not free the Kremlin of responsibility for violation of territorial integrity, a lawyer of the Verkhovna Rada Committee on Foreign Affairs, Oleh Vasylenko, has said.

"Through its actions, temporarily occupying part of the territory of Ukraine - the Autonomous Republic of Crimea and Sevastopol, continuing armed aggression and financing terrorist organizations in certain areas of Donetsk and Luhansk regions of Ukraine, continuing interference in the internal affairs of Ukraine, Russia grossly violates the terms of the Treaty," he told Interfax-Ukraine on Wednesday.

The lawyer said that in this connection it is possible to follow Russia's logic on denunciation of the treaty and regard such actions by Moscow as an attempt to avoid responsibility in the future.

According to Vasylenko, international law and the Vienna Convention indicate that the termination of the treaty does not affect the rights, obligations and legal status of the participants arising as a result of its implementation or non-implementation until the termination of such a treaty.

"All illegal actions by Russia with respect to encroachment on the territorial integrity and sovereignty of Ukraine started during the effect of the treaty, therefore, Russia's steps to terminate the treaty will not have a significant influence on Ukraine's position in international judicial institutions, especially given that most lawsuits have already been submitted and are at different stages of consideration," Vasylenko said.

In addition, he said, if Russia decides to terminate the treaty, it must fulfill its procedural obligations and conduct preliminary consultations or negotiations, in accordance with the Vienna Convention and the provisions of the treaty itself.

On January 14, 2018, Russian media quoted First Deputy Chairman of the Russian State Duma Committee on CIS Affairs Konstantin Zatulin, who proposed revising the Treaty on Friendship and Cooperation between Russia and Ukraine. In particular, he believes that part of the treaty, which refers to the recognition of territorial borders by the countries, is "unilaterally beneficial" to Ukraine.

Zatulin sid that when ratifying the treaty in 1999, Russia confirmed that Crimea and Sevastopol were part of Ukraine.

"Our interpretation of the treaty is that the recognition of borders is interlinked with friendship, cooperation and partnership. That is, if there is no friendship, there is a reason to resolve all issues anew, including issues on the borders," he said.

The Russian Foreign Ministry said in a statement in connection with the 20th anniversary of the treaty in June 2017 that "the very existence of this document serves as a guarantee of the existence of a foundation for the revival of bilateral relations."

The Treaty on Friendship, Cooperation and Partnership between Ukraine and Russia was signed on May 31, 1997 for a period of ten years (with subsequent automatic extension of the document if the parties do not object). The Verkhovna Rada ratified the treaty on January 14, 1998, and the State Duma on December 25, 1998. The treaty came into force on April 1, 1999 (since the exchange of instruments of ratification).

According to Article 40 of the treaty, it is concluded for a period of ten years. The validity of the contract is automatically extended for the next ten-year periods if neither side declares its desire to terminate it at least six months before the expiry of the next ten-year period. The period of the first ten-year period began from the date of entry into force of the treaty (from April 1, 1999) and ended on April 1, 2009. Then neither side expressed its desire to terminate the treaty before October 1, 2008, so its effect was automatically extended for the next ten-year period.

The Treaty on Friendship, Cooperation and Partnership between Russia and Ukraine secured the principle of strategic partnership, recognition of the inviolability of existing borders, respect for territorial integrity and mutual obligation not to use its territory to the detriment of each other's security.