The Bush administration hopes the agreement will form the cornerstone of a closer relationship with a democratic, economically vibrant country that borders nuclear-armed China.

After months of deadlock, India is confident it now has the political support at home for the deal. But it could be weeks, or even months, before the accord is taken up by crucial international organizations and, if approved, is then sent to the US Congress for final approval.

By then, American lawmakers probably would have only a handful of days left in their legislative calendar. The lack of time even has supporters sceptical about the immediate future of the deal, which would allow shipments of atomic fuel and technology to India.

"There's not that many days left to do this, assuming they act yesterday," Democratic Rep. Gary Ackerman, chairman of the House of Representatives Foreign Affairs Subcommittee on South Asia and the self-described "lead cheerleader" for the deal, said in an interview. "It's not impossible but highly unlikely that they've done this thing in time."

The next US president could take up the accord when he takes over in January. Failure to secure approval under Bush, however, would leave it to an uncertain fate. Both leading candidates for president, Democrat Barack Obama and Republican John McCain, have indicated support for the deal, but it is not clear that either would consider it a priority as president. The new administration also would be working without many of the high-level Bush officials who led painstaking talks with India and then persuaded skeptical US lawmakers to give their approval.

Christine Fair, a South Asia specialist at the RAND Corp., said that "the underbelly of this deal, as Bush envisioned it, was that, with our help, India was going to become a global power, and that meant becoming a global nuclear power. I just don't know if McCain or Obama are going to embrace that."

Bush has argued that the nuclear deal would empower a friendly democracy that has demonstrated what he sees as nuclear responsibility. The deal would reverse three decades of US policy on India, which has not signed international nonproliferation accords but has tested nuclear weapons. India, in exchange for much-needed energy support, would open its civilian, but not its military, reactors to international inspections.

Indian Prime Minister Manmohan Singh's communist allies have withdrawn their support for his coalition government to protest his plan to push forward with the nuclear deal. Those communist parties were not part of Singh's coalition, but the government counted on those parties' lawmakers for a majority in parliamentary votes.

Singh said this week, however, that he was able to secure alternative support from new allies that would allow the communists to walk away and still keep the deal and his government afloat.

Despite Singh's political maneuvers, the agreement still must be approved by the International Atomic Energy Agency, the UN nuclear watchdog organization, and the Nuclear Suppliers Group of countries that export nuclear material. The IAEA could meet on the issue by the end of this month, but the U.S. Congress has only a few remaining weeks of work left in July.

Lawmakers will be campaigning for November elections in their home districts in August and return to Washington for a few weeks in September before they again resume campaigning. Ackerman's staff estimates that about 30 legislative days remain, and many of those will be devoted to pushing through measures necessary to keep the government running. Democratic House Speaker Nancy Pelosi has said there will not be an extra legislative session after Nov. 4 elections but before newly elected lawmakers take office in January.

"There are a lot of uncertainties," said Ashley J. Tellis, a senior associate at the Carnegie Endowment for International Peace who served as an adviser to former Undersecretary of State Nicholas Burns, a top negotiator on the deal. "It's going to be tight, if only because we are in the second half of an election year."

Critics say the deal would ruin global efforts to stop the spread of atomic weapons and boost India's nuclear arsenal.

Democratic Rep. Ed Markey, a leading critic, said the Bush administration is pressuring the IEAE and NSG for quick approval of the deal. That, he said, compromises the integrity of the review process of the deal's nonproliferation implications. If Congress cannot ratify the deal, and the IAEA and NSG approve it, Markey added in an interview, "nothing would stop India from signing deals with other international suppliers."