Forty-five nuclear supplier states on Saturday approved a US proposal to drop a ban on trade with India, advancing a US-Indian atomic energy deal, diplomats in the closed meeting told Reuters.

The decision followed a tense debate over conditions for the move demanded by Nuclear Suppliers Group (NSG) members to minimise any damage to the Non-Proliferation Treaty, which India has not joined. Details were not immediately known.

One hurdle remained before the US-India deal could take force - ratification by the US Congress. It must act before adjourning in late September for elections or the deal could be left to an uncertain fate under a new US administration.

NGG adopted a one-off waiver allowing them to do business with India after several small states agreed under heavy US pressure to weaker language than they had sought to ensure India does not test atom bombs again.

After two weeks of feverish meetings and long-distance consultations, resistance to the exemption finally crumbled when six holdout states reluctantly accepted an Indian declaration on Friday reinforcing a commitment to a voluntary test moratorium.

It also said India - whose regional rival Pakistan also has nuclear firepower outside the NPT - would not join any future nuclear arms race, would permit broader UN inspections and adhered to the NSG anti-proliferation export control regime.

'Based on commitments in the political declaration of (India's foreign ministry), 'participating states have decided on the following policy' - the unprecedented waiver, the final of several revised US drafts for the move read.

'But for the first time in my experience of international diplomatic negotiations, a consensus decision was followed by complete silence in the room. No clapping, nothing,' a European diplomat in the Vienna gathering said.

'It showed a lot of us felt pressured to some extent into a decision by the Americans and few were totally satisfied.'

Diplomats said the final draft cited only the need for a special NSG meeting if India reneged on its commitments.

'The problem here is that the NSG works only on the basis of consensus. So if India did another test the follow-up meeting could be reduced to a talkshop by any one member like the Americans,' said another diplomat. 'It's not clear we could take action as a group.'

NSG critics and disarmament campaigners fear Indian access to nuclear material markets will let it tap into more of its limited indigenous resources, such as uranium fuel, to boost its nuclear arsenal, and drive Pakistan into another arms race.

Intense US pressure for the waiver involved overnight phone calls to presidents and prime ministers of holdout countries, several diplomats said.

Six NSG nations had been demanding a clause stipulating an automatic cessation of the waiver if India tested another bomb.

After India's statement, the holdout group splintered as Norway, the Netherlands and Switzerland indicated they could accept more limited language, diplomats said. Ireland, Austria and New Zealand fell into line on Saturday.-Reuters