WASHINGTON — Even with India’s last-minute revival of a languishing civil nuclear accord with America, it may be too late for an election-year Congress to ratify what has been one of President Bush’s top foreign policy initiatives.

The 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 necessary 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 Congress for final consideration.

By then, American lawmakers probably would have only a handful of days left in their legislative calendar. The lack of time even has supporters skeptical 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,” the chairman of the House of Representatives Foreign Affairs Subcommittee on South Asia and the self-described “lead cheerleader” for the deal, Rep. Gary Ackerman, said in an interview. “It’s not impossible but highly unlikely that they’ve done this thing in time.”

The next president could take up the accord when he takes over in January. Failure to secure approval under Mr. Bush, however, would leave it to an uncertain fate. Both leading candidates for president, Senators Obama and 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 American lawmakers to give their approval.