US Defence Secretary Robert Gates said Monday that the US would be an "active participant" in South-East Asian security issues, DPA reported.
In a speech to army officers and students in Hanoi, Gates praised US-Vietnamese military cooperation and stressed the importance of multilateral institutions in security issues.
"Increasingly, we find that relying exclusively on bilateral relationships is not enough - we need multilateral institutions in order to confront the most important security challenges in this region," he said.
Gates was in Hanoi for a meeting of regional defence ministers that has drawn attention because of tensions between the US, China, and South-East Asian nations over the South China Sea. China claims most of the sea as its own, and has seized hundreds of Vietnamese fishing boats in recent months.
His emphasis on multilateral institutions echoed statements by US Secretary of State Hillary Clinton in July that the US would support multilateral negotiations between China and the Association of South-East Asian Nations (ASEAN).
The US approach has been interpreted as taking Vietnam's side in the disputes with China. Beijing prefers to negotiate bilaterally with each country that disputes its maritime claims.
A student at Vietnam National University asked how ASEAN members could be sure that the US was a reliable partner who would not "just walk away when her national interests are served."
"The US has been active in Asia for more than 150 years," Gates said. "We intend to be an active participant not only in economic matters, but also in defence and security matters."
The first-ever ASEAN Defence Ministers' Meeting Plus brings together the 10 members of the Association of South-East Asian Nations along with China, the US, Japan, South Korea, India, Russia, Australia and New Zealand.
Gates was scheduled to meet separately with his Vietnamese counterpart, Phung Quang Thanh, and Chinese defence chief Liang Guanglie.