President Barack Obama has approved a civilian nuclear pact with Vietnam which could lead to the sale of US reactors to Washington's energy-hungry former war foe.
The move by the president formally opened a 90-day review process in Congress. If no legislation is passed contravening the accord, it will then come into force.
Under the accord, US officials said, Vietnam committed not to produce radioactive ingredients for nuclear weapons and signed up to US nonproliferation standards, which the White House bills as the strongest in the world.
"I have determined that the performance of the agreement will promote, and will not constitute an unreasonable risk to, the common defence and security," Obama said in a memorandum to the Energy Department.
Vietnam agreed not to enrich or reprocess uranium, key steps in the manufacture of nuclear weapons, in the deal signed on the sidelines of an East Asia summit in Brunei in October.
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It also pledged to seek components for its fuel cycle on the open, international market.
Vietnam's market for nuclear power - already the second largest in East Asia after China - is expected to grow to $US50 billion ($A55.84 billion) by 2030.
Vietnam faces energy shortages and is pursuing nuclear energy, officials have said, with a plan that calls for the first nuclear power plant to be in commercial operation by 2020.
It wants nuclear energy to provide more than 10 per cent of its total power generation needs by 2030.
The communist-ruled nation already has a nuclear co-operation agreement with Russia.
Despite Hanoi's determination to pursue nuclear power, there has been domestic opposition with many voicing fears that the locations selected for the plants make them vulnerable to earthquakes or tsunamis.
