Last year's multi-billion dollar deal has got bogged down by issues such as accident liability protection for US companies which have lobbied hard for a slice of India's lucrative nuclear market.

Former US President George Bush signed the agreement with Prime Minister Manmohan Singh in the face of domestic critics who said it violated the nuclear Non-Proliferation Treaty (NPT).

The deal, which will give India access to high-end technology and nuclear fuel for its reactors, brought India out of 30 years of nuclear isolation.

But the Indian government has so far only allocated sites for the construction of nuclear installations to France and Russia.

Both those governments shield their companies from liability for an industrial accident, unlike the United States, and American companies want New Delhi to help lift the burden.

"Two other countries have already been given sites and the American industry is getting very restless about the delay because they're anxious to get going," Ambassador David Mulford said at a conference in New Delhi.