Washington - The United States and Vietnam on Monday opened their first formal military relationship since their war which ended in 1975.

The US and Vietnamese militaries signed a Statement of Intent on Military Medical Cooperation in Hanoi establishing cooperation in health, setting the stage for exchanges and research cooperation in military medicine, a US Navy statement said.

The former foes have been steadily building ties and last month held a joint naval drill. But Monday's agreement marks the first formal military cooperation since the normalization of diplomatic relations in 1995, the navy said.

Vice-Admiral Adam M. Robinson Jr, the US Navy's surgeon general, said that the agreement was not about politics and that the US hoped for more cooperation on health issues around the region.

"Medicine and medical research are universal languages that all countries and cultures understand. Diseases affect us all in the same way," Robinson said.

Discussions on the agreement began with a meeting in November 2009 between Robinson and Vietnamese Lieutenant General Chu Tien Cuong, who was then the director of the Military Medical Department of Vietnam, at the annual Association of Military Surgeons of the United States conference in St Louis.

However, the US described last week's exercises off Vietnam's central coast as non-combat, saying they focused on areas such as navigation and maintenance.

The relationship between Vietnam and the US has shown signs of heating up quickly, and has been strengthened by a series of navy drills last August and in July this year, according to Chu Hao, researcher on Vietnamese studies at China Institutes of Contemporary International Relations.

"But the military trust between the two countries is not very solid, so they chose to begin their cooperation in areas that are not so sensitive, such as health," he told China Daily.

Besides pragmatic reasons, with Vietnam getting closer to the US to further develop its domestic export-driven economy and technology, the other major strategic concern for Vietnam to strengthen its ties with the US is to pursue the balance of power as China's impact is growing in the area, Chu said.

"Although the agreement may sound more like a symbolic deal, it indicates some concrete progress being made by the two countries," he noted.