Other signs of cooperation between the former combatants include new business sales, more military cooperation, research programs involving universities in both countries and cultural exchanges that include the introduction of the U.S. Peace Corps to Vietnam, Obama said.

The arms embargo is one of the last major vestiges of the Vietnam War era. The US has not indicated publicly it would remove the embargo and has long said such a move would depend on Vietnam showing progress on human rights.

The Vietnamese Ministry of Foreign Affairs said Vietnam had no intention of forming military alliances “against other countries” and its policy was about self-defence.

“The procurement of defence equipment by Vietnam from partner countries is completely normal,” he added. “We are not allied or linking militarily with any country against other countries.”

Vietnam has been in talks with Western and US arms manufacturers to boost its fleet of fighter jets, helicopters and maritime patrol aircraft, although Russia, its traditional supplier, has a dominant position.