The US Senate approved the deal on Wednesday, ending a three-decade ban on nuclear trade with Delhi.

But Ms Rice said there were "a lot of administrative details" to be sorted out before it could be signed.

India says the deal is vital to meet civilian energy demands, but critics say it undermines efforts to control the spread of nuclear weapons.

Speaking on her way to Delhi, Ms Rice said it was not certain whether she would sign the deal on her visit.

But she said she wanted to "draw a line under this one way or another" and move on to other efforts to build a relationship which had made "extraordinary progress" and had "a firm foundation to reach its full potential".

She said the agreement "removes for India a barrier to full integration on a whole range of technologies".

Prime Minister Manmohan Singh has said the deal will help India to liberate itself from "the constraints of technology denial of 34 years".

The BBC's Kim Ghattas in Washington says the Bush administration has lobbied hard in Congress to get the deal approved but that wary lawmakers insisted on certain amendments, which may upset the Indians.

Treaty 'undermined'

Mr Singh has had a rough ride over the agreement in India from critics who say it will bring the country's foreign policy too much under US influence.

The deal, which has been approved by the UN's nuclear watchdog the International Atomic Energy Agency, gives India access to US civilian nuclear technology and fuel in return for inspections of its civilian, but not military, nuclear facilities.

It ends a boycott imposed by nuclear supplier states because India has not signed the Nuclear Non-Proliferation Treaty (NPT).

BBC world affairs correspondent Paul Reynolds says the deal is the best of a bad situation for some, including the IAEA, as it will subject India to a more substantial inspection regime than at present.

But critics say it undermines the NPT because it effectively acknowledges that India has nuclear weapons while not being a signatory to the treaty.

They argue it sets a bad example for countries like Iran and will spark off a nuclear arms race in Asia.

The Bush administration has made the deal one of its key foreign policy achievements and hopes the agreement will bolster ties with India which were cooled during the Cold War, says our correspondent in Washington.

America has restricted nuclear co-operation with India since 1974, after it tested a nuclear weapon.

The US state department said Ms Rice will meet various Indian leaders during her brief visit, including Mr Singh and External Affairs Minister Pranab Mukherjee, before travelling to Kazakhstan.

BBC