SOFIA, June 19 (Xinhua) -- Some 400 U.S. troops along with Bulgarian units on Tuesday began a military drill at Novo Selo Training Area, which will last until Oct. 30, Bulgarian Defense ministry said in a statement.

Tanks M1A2 Abrams, armored vehicles M2A3 Bradley and APC M113, as well as self-propelled howitzers M109A6 Paladins, would be used during the exercise codenamed "Joint Training 2," the statement said.

It noted the drill was "part of the measures to strengthen security in the Black Sea region."

Bulgaria, a NATO member since 2004, signed a defense cooperation agreement with the United States in 2006.

According to the agreement, the United States may deploy defense equipment and no more than 2,500 personnel to the Novo Selo Training Range, the Aytos Storage facility, Bezmer Air Base, and Graf Ignatievo Air Base, and use these facilities for activities such as security cooperation exercises, refueling of aircraft, and temporary maintenance of vehicles.