Rice was in New Delhi days after the U.S. Congress approved a proposal to lift an export ban on nuclear materials to India, potentially opening up billions of dollars in U.S. investment the country's infrastructure. But Rice said it's not certain a deal will be signed on the trip, the BBC reported.

There were "a lot of administrative details" to be sorted out before it could be signed, she told the broadcaster, adding she wanted to "draw a line under this one way or another" and move on to other efforts. Rice said the U.S.-India relationship had made "extraordinary progress" and had "a firm foundation to reach its full potential."

Prime Minister Manmohan Singh told reporters that the deal will help India to emerge from "the constraints of technology denial of 34 years," but, because India refuses to sign the nuclear non-proliferation treaty, a condition of the deal is that it must accept international oversight of its civilian nuclear activities.

India's military nuclear activities will not be monitored under the deal.