Vietnam said Wednesday it had not yet begun negotiating with the United States on sharing nuclear fuel and technology, despite Washington saying talks were ongoing.

"Vietnam and the United States have not yet carried out negotiations on a peaceful uses of nuclear energy agreement," foreign ministry spokeswoman Nguyen Phuong Nga said.

Washington said Thursday it was in talks with its former Cold War foe over civilian nuclear technology, but declined to say whether Hanoi would be allowed to enrich its own uranium, as reported in the Wall Street Journal.

Congressional critics of the deal said the terms would undercut the more stringent demands placed on US partners in the Middle East, which had renounced uranium enrichment in exchange for nuclear cooperation, the Journal reported.

State Department spokesman Philip Crowley said Thursday that the deal did not involve China, Vietnam's neighbour and ally.

But he refused to comment on the enrichment issue, saying only that "we do want to see... fewer countries enriching uranium around the world".

The United Arab Emirates signed a nuclear cooperation deal with the United States last year under which the UAE agreed not to enrich uranium.

In June this year the UN Security Council launched fresh sanctions against Iran over its nuclear programme and in particular its refusal to freeze uranium enrichment.

The US and Vietnam signed a memorandum of understanding in 2001 to pursue cooperation on securing fissile materials and developing civilian nuclear power, and signed a further cooperation accord in March.

Vietnam is seeking to make nuclear power a key energy source and in June announced an expansion of its programme, with eight plants planned for operation over the next 20 years.