Vietnam supports U.S. "intervention" in the Asia-Pacific if it helps keep peace and stability, the defense ministry said, in a timely endorsement of a continued U.S. presence amid uncertainty over Washington's faltering "pivot".

Vice defense minister, Senior Lieutenant-General Nguyen Chi Vinh, met on Monday with Cara Abercrombie, the U.S. Deputy Assistant Secretary of Defense for South and Southeast Asia, and told her Vietnam backed a positive U.S. role.

The general's words of support, conveyed by the defense ministry, come when the United States most needs them, with its "rebalance" - aimed at boosting its Asian foothold and tempering China's rise - now under strain in the run-up to a U.S. presidential election.

Vinh "affirmed that Vietnam will support the U.S and other partners to intervene in the region as long as it brings peace, stability and prosperity", it said in a statement.

At the dialogue, Abercrombie said the United States would not change its rebalance strategy, the statement added.

Uncertainty lingers in Asia over changes ahead at the White House and whether a new leadership would give less priority to keeping China in check as it grows increasingly assertive in the East Vietnam Sea, a waterway vital to global trade.

Washington's traditional defense alliances in Southeast Asia are currently being tested, with ties with Thailand frosty since a 2014 coup and questions about the future of a tight military relationship with the Philippines under volatile new President Rodrigo Duterte, a staunch U.S. critic.

Relations between the United States and Vietnam, in contrast, have warmed substantially in the past two years, much to do with jitters over the East Vietnam Sea to which Hanoi has disputes with Beijing.

The latest affirmation of those ties came after the full lifting of a U.S. lethal arms embargo on Vietnam in May, allowing closer defense links and some joint military exercises between the former enemies.

Two U.S. warships earlier this month made a call at a new international port built at Vietnam's strategic Cam Ranh Bay in a brief but symbolic return for U.S. combat vessels.

The U.S. ambassador to Vietnam last week admitted the U.S. dynamism once seen in the region had "a little bit diminished", but said there was still appetite for U.S. involvement.

Ted Osius also said a dramatic change in U.S.-Vietnam ties was "not about to happen" because of Philippine leader Duterte's outreach toward China.