ISTANBUL (Reuters – Turkey called Russia’s invasion of Ukraine a “war” on Sunday, in a shift in rhetoric that could allow NATO member nations to enact an international pact limiting Russian maritime passage to the Black Sea.

According to the 1936 Montreux Convention Turkey holds the Dardanelles, Bosphorus and Black seas straits. It can restrict the movement of warships in wartime or when threatened.

Ankara, balancing its Western commitments with close ties to Moscow has declared that Russia’s attack on Turkey is unacceptable. But it had not yet called the situation a war.

“On the fourth-day of the Ukraine War, we reiterate President (Tayyip Erdogan’s) call for an urgent halt to Russian attacks and the commencement of ceasefire talks,” Ibrahim Kalin (NYSE:) stated on Twitter.

Turkey’s communication director Fahrettin Altun said that “we are witnessing another war in the region” and reiterated Erdogan’s offer of mediation

Kyiv appealed for Ankara’s assistance in stopping any Russian warships passing towards the Black Sea. This is where Moscow launched its invasion on Ukraine’s south coast.

However, Turkey’s Foreign Minister stated Friday that Russia has the rights under Montreux to bring ships back to their base. This could restrict any Turkish policy shift.

Turkey enjoys good relations with Russia and Ukraine. Moscow’s heavy energy and commodities imports as well its tourism sector could be damaged by any move against Moscow.