US Assistant Secretary of Defense for International Security Affairs Peter Rodman met Vice Minister of Defense General Nguyen Huy Hieu, the Vietnamese defense ministry told AFP.

"They discussed bilateral, regional and international issues of common concern during the meeting," an official said, refusing to elaborate.

Rodman's visit comes a fortnight before Prime Minister Khai is to meet US President George W. Bush in Washington on June 21.

Khai's historic trip, the first by a Vietnamese head of government since the end of the Vietnam War in 1975, will follow a 2000 visit by then US president Bill Clinton, the highest-level exchange since the war.

Analysts in Hanoi said the two countries were considering signing a security cooperation agreement.

Such an accord could, however, raise the hackles in Vietnam's giant neighbour China, a possibility Hanoi would be anxious to avoid.

"The key issue here is how far to go with the United States without arousing concern in China," said Carl Thayer, an Australian expert on Vietnam affairs.

"The visit by Prime Minister Khai should provide an indication of Vietnam's readiness to sign on to the International Military Education and Training programme with the US Defense Department," he added.

The US deputy chief of mission in Vietnam, John Boardman, said at the weekend that bilateral military contacts had "moved ahead in very positive ways".

"Our two militaries are cooperating and engaging in a growing number of important areas, ranging from supporting humanitarian assistance and disaster relief to co-hosting a major, multinational, regional military medical conference," Boardman said at a forum on US-Vietnam relations.

"We are developing an important and solid relationship with the People's Army of Vietnam, one that no doubt makes the region a more stable and secure place to live and do business in," the senior diplomat said.