Turkey has taken a strong stance by preventing warships from passing through the Black Sea under the Montreux Agreement, the United States Under Secretary of State for Political Affairs, Victoria Jane Nuland said Tuesday, reports TurkicWorld with the reference of DailySabah.

Nuland made statements about Turkey's Montreux decision and Poland's decision to send warplanes to Ukraine in the session on Ukraine in the Senate Foreign Relations Committee.

Stating that Russian President Vladimir Putin's installation of more weapon systems in Crimea is a cause for concern and that it threatens the free movement of ships in a large part of the Black Sea, Nuland noted that they periodically conduct U.S. and NATO exercises to demonstrate their presence there.

Nuland said: "We are trying to keep the Black Sea open, on the other hand, we are working with Romania, Bulgaria and Turkey. Since the conflict started, Turkey (in Ukraine) has taken strong steps to prevent the passage of warships under the Montreux Convention. We are working on these issues."

Under the 1936 Montreux Convention, NATO member Turkey has control over the Bosporus and Dardanelles straits, linking the Mediterranean and Black seas. The pact gives Ankara the power to regulate the transit of naval warships and to close Turkish Straits to foreign warships during wartime and when it is threatened.

Turkey has called Russia's invasion of Ukraine a "war" in a rhetorical shift that opened the way for the move.

Maintaining its neutral and balanced stance, Turkey continues its diplomatic efforts to de-escalate the Ukraine conflict, urging all sides to exercise restraint. While Ankara has opposed international sanctions designed to isolate Moscow, it also closed its straits to prevent some Russian vessels from crossing the Turkish Straits.

NATO ally Turkey borders Ukraine and Russia in the Black Sea and has good ties with both. Since the beginning of the conflict, Ankara has offered to mediate between the two sides and host peace talks, underlining its support for Ukraine’s territorial integrity and sovereignty. Having recently called Russia’s invasion an unacceptable violation of international law, Turkey has carefully formulated its rhetoric not to offend Moscow, with which it has close energy, defense and tourism ties.

Foreign Minister Mevlut Chavushoglu said Monday that Ukrainian and Russian foreign ministers will meet in Antalya on Thursday as part of Turkey's mediation efforts to find a solution in the face of Moscow's invasion.