In bid to increase further tensions, the Ukrainian parliament, voted on Thursday not to extend the country's treaty of friendship with Russia, after it terminates on April 1, 2019. A total of 277 parliamentarians out of 450 voted to terminate the treaty by allowing it to expire.

The Russia-Ukraine Treaty on Friendship, Cooperation and Partnership, signed in 1997, obliges Russia and Ukraine to "respect the territorial integrity of each other and confirm inviolability of current mutual borders," as reported by RFE/RL.

Relations between the two neighbors have been strained further following a Nov. 25 incident in which the Russian coast guard fired upon and seized three Ukrainian naval vessels and their crews off the Crimean Peninsula that Russia annexed from Ukraine. Ukrainian President Petro Poroshenko responded by introducing martial law for 30 days in much of Ukraine. For the duration of martial law, Ukrainian authorities barred entry to all Russian males aged 16 to 60 in a move the Ukrainian leader said was needed to prevent Russia from further destabilizing the country.

Turkish President Recep Tayyip Erdoğan on Friday said that he expects "positive" steps from Russia and Ukraine to resolve recent tensions between the two countries. Speaking to reporters in Istanbul, President Erdoğan said: "I held a phone conversation with [Russian President] Mr. [Vladimir] Putin in this regard, held an inter-committee meeting in Argentina and I also spoke with [Ukrainian President] Mr. [Petro] Poroshenko over the phone." "I hope they [Russia and Ukraine] will have a positive approach," Erdoğan said, and added "I think there is an investigation going on" over the detention of Ukrainian sailors. "We can only make a request, we cannot go further," President added.

Following the naval confrontation in the Black Sea, an unarmed U.S. Air Force plane with American and international observers flew a special flight over Ukraine Thursday in a show of solidarity with Ukraine. In a statement, the Pentagon called it an "extraordinary" flight under the Open Skies Treaty, which is an international accord that gives each member country the right to conduct, and the obligation to accept, unarmed military observation flights. Eric Pahon, a Pentagon spokesman, said this was the first "extraordinary" Open Skies flight since 2014 in response to Russia's annexation of Crimea.

The move came after the Pentagon's request from Turkey for the intent to send a warship into the Black Sea through the Bosporus and the Dardanelles. The transit would be another signal of military support for Ukraine. U.S. Navy ships routinely sail in and out of the Black Sea, and under international rules are only allowed to stay in the waters for 21 days. The most recent was the fast transport ship USNS Carson City, in September. Officials wouldn't say which ship would make the passage in mid-December.