The U.S. Navy will keep a regular presence in the Black Sea, the U.S. Naval Forces Europe-Africa said in a press release Thursday. The announcement, made during a large NATO drill that includes Ukrainian forces, is likely to anger Russia, which borders the sea and has a fleet there. 

"Over the past year, we have sustained a presence in the Black Sea, even as we operate consistently in the Mediterranean," said Vice Adm. James Foggo, deputy commander of U.S. Naval Forces Europe, during a Tuesday briefing with reporters in Odessa, Ukraine. "We are making our presence in the region 'normal,' and we are conducting regular and frequent exercises and engagements with navies in the area."

The Black Sea has become a strategic area of operations for NATO forces since Russia annexed Crimea from Ukraine and began supporting separatist rebels early last year. The body of water washes the shores of Ukraine, Crimea and Russia, as well as Turkey, Georgia, Romania and Bulgaria. It connects with the Mediterranean Sea that enables access out to the Atlantic Ocean and through the Suez Canal to the Red Sea and the Gulf of Aden. While NATO member Turkey controls access, Russia has significant power in the area from its naval bases and ports.

Foggo arrived in Odessa to inspect the USS Donald Cook before it took part in Sea Breeze 2015, exercises that began Monday.

"We’ve tried to maintain near-continuous presence in the Black Sea because it is an important region," said Foggo, whose fleet entered the sea in July for Exercise Breeze and Exercise Sea Shield, and Exercise Trident Poseidon in May.

Under a 1936 treaty, the Montreux Convention, vessels belonging to countries that don't have Black Sea coastlines can stay in the area for only 21 days at a time and must be under 15,000 tons, which means large destroyers, frigates and aircraft carriers are prohibited from entering. Since Russia is on the Black Sea, it has a significant advantage. 

The current NATO exercise taking place in the Black Sea includes ships from Bulgaria, Germany, Greece, Italy, Moldova, Romania, Sweden, Turkey, Ukraine, the United Kingdom and the United States.

Over the last 18 months, since Moscow annexed Crimea and fueled the war in eastern Ukraine, NATO has fallen back into military postures not seen since the end of the Cold War in 1991. The conflict has killed more than  7,000 people since it began in April 2014.