The US Congress, following a strong Senate vote, aims to complete work in early December on legislation to allow nuclear co-operation with India for the first time in three decades.
An overwhelming majority has now endorsed separate versions of the bill in both the Senate and US House of Representatives, although different wording, including on nuclear-armed India's ties to Iran, could cause problems.
Still, supporters are optimistic the bills can be reconciled in negotiations between the two chambers and given final passage before the "lame duck" Republican-led Congress surrenders power to Democrats in January.
"I am confident that we can now work closely with our colleagues in the House to get this important measure to the President (George W. Bush) as swiftly as possible," Senate Majority leader Bill Frist, a Tennessee Republican, said in a statement after Thursday's 85-12 Senate vote.
The 45-nation Nuclear Suppliers Group and the International Atomic Energy Agency still have to approve the agreement that would allow New Delhi to purchase US nuclear fuel, reactors and related technology.
The US Congress gets another chance to vote on the deal, probably next year, because it must approve technical details.
Bush and his administration argue nuclear co-operation is essential to relations between the world's largest democracies that will be pillars of security in the 21st century.
Opponents contend the agreement harms US security by allowing New Delhi to expand its nuclear weapons arsenal, by fostering an arms race in Asia among India and nuclear rivals Pakistan and China and by undermining decades of US non-proliferation policy.
Rep. Joseph Crowley, a New York Democrat who expects to be a House negotiator with the Senate, said New Delhi is unhappy with a Senate provision requiring Bush to certify that India is "fully and actively" participating in efforts to contain Iran's nuclear program before US-India nuclear co-operation could proceed.
The House version addresses the issue in a way that is "less offensive to the Indians and yet serves the same purpose," he told Reuters.
But, he added: "I think we will be able to work something out."
Secretary of State Condoleezza Rice said she looked forward to the House-Senate negotiations "when remaining issues of concern to the US government can be addressed." She did not specify those concerns.
"This initiative will help India meet its growing energy needs, enhance co-operation on energy security and non-proliferation, and increase economic investment opportunities," she said in a statement.
She also stressed the need for both sides to fully meet their commitments.
Daryl Kimball of the Arms Control Association and a leading opponent of the nuclear deal called the Senate bill a "great mistake for security and non-proliferation policy."
But the Senate version is better than the House version because it bars transfers of technology related to uranium enrichment, reprocessing and heavy water production, which can aid nuclear weapons production, he told Reuters.
He said the nuclear agreement still faced substantial hurdles. "This is far from over." Kimball said.