Bush and Manmohan Singh, the Indian prime minister, had agreed to the deal in July last year when Singh paid a visit to Washington. They  reaffirmed it during the US leader's visit to New Delhi in March.

 

Controversial bill

 

The agreement was seen as controversial because the US congress  had to create a rare exception for India from some of the requirements of the US Atomic Energy Act, which currently prohibits nuclear sales to non-NPT signatories.

  

In addition, US weapons experts said that forging such an agreement with non-NPT member India would not only make it harder to enforce rules against countries such as Iran and North Korea, but also set a dangerous precedent for other countries with nuclear programmes.

  

Richard Lugar, a Republican senator and co-author of the bill, said: "This agreement is the most important strategic diplomatic initiative undertaken by President Bush."

 

US officials say the Bush administration had won a commitment from New Delhi to negotiate a so-called Fissile Material Cutoff Treaty, as part of a multilateral approach to reduce nuclear tension surrounding any potential arms race in South Asia.

  

The US House of Representatives approved the nuclear deal in July, but a senate vote had been delayed due to the US midterm elections last week that resulted in Democratic party control of both chambers in the new congress from January.

 

The senate and the House are scheduled to meet next month to  reconcile several amendments they had made and that need to be  approved again by the two chambers before Bush signs the final bill into law.