"The exercise is using essentually the major training facilities that the US has been interested in -- Bezmer and Novo Selo," Pardew told a press conference.

"It shows what will happen when negotiations (for using them) have completed an agreement" this fall, he added.

Bulgaria would be used as a staging post for moving troops based in Europe to a deployment further east, which is better suited to the current US preoccupation with terrorism and conflicts in the Middle East.

The United States has requested the use of three bases in Bulgaria -- the Novo Selo training range near Sliven, to the south-east, the Bezmer air base near Yambol, to the southeast, and the third in the Black Sea port city of Bourgas.

"The exercise is also designed to improve readiness and interoperability" within the North Athlantic Treaty Organisation (NATO), exercise director US Brigadier General Michael Tucker said Wednesday.

"This is our second bilateral army exercise together with the Bulgarians and is an important part of our ongoing efforts to strengthen our military ties and to learn from each other," Tucker added.

Bulgaria joined NATO in 2004 and has since strived to reform its armed forces and improve equipment to live up to alliance standards.

"We will conduct a series of training opportunities together, including weapon shooting ranges, small unit manoeuvres -- all under simulated combat conditions" with a variety of ground vehicles and aircraft from both armies involved, Tucker added.