The US Senate has overwhelmingly voted to pass a controversial deal to share civilian nuclear technology with India.
Energy-hungry India needs nuclear power
Under the deal, which was proposed more than a year ago, India must allow international inspections of its nuclear facilities.
US President George W Bush hailed the move as bringing India into the "nuclear non-proliferation mainstream".
However, the bill still has to clear a number of hurdles before it becomes law and is implemented.
One condition would require India to fully and actively participate in efforts to contain Iran's nuclear programme.
The BBC's Shahzeb Jillani in Washington says critics believe America should not be rewarding India for having secretly developing a nuclear weapons programme and refusing to sign the Nuclear Non-Proliferation Treaty (NPT).
The Senate bill and a version passed by the House of Representatives, the lower house of the US Congress, must now be reconciled and approved by Mr Bush before the legislation can take effect.
"As India's economy continues to grow, this partnership will help India meet its energy needs without increasing air pollution and greenhouse gas emissions," Mr Bush said.
The Senate adopted the bill by 85 votes to 12 after a series of proposed amendments - which India had opposed - were defeated.
There had been strong opposition to the deal because of fears it could encourage the spread of nuclear weapons.
India's Foreign Affairs Minister Pranab Mukherjee welcomed the passage of the bill, saying it reflected "very broad bipartisan support".
The deal is a "lasting incentive" for India not to test nuclear weapons and "to co-operate closely with the United States in stopping proliferation", Senator Richard Lugar said as the Senate debate began.
Correspondents say that once the legislation is eventually approved, the initiative will overturn decades of US anti-proliferation policy.
But several obstacles loom before the two countries can begin trade in civilian nuclear materials.
India would need to get approval for the deal from the Nuclear Suppliers Group, an assembly of nations that export nuclear material.
Delhi would also need to negotiate a safeguard agreement with the UN nuclear watchdog, the International Atomic Energy Agency (IAEA).
There is also some concern about the transfer of missile technology to Iran by at least two Indian firms, recently black-listed by the US government.
Once those hurdles have been overcome, technical negotiations would need to be completed between the two countries before Congress holds another vote on the deal.
Overall, the agreement has enjoyed strong bipartisan support among US lawmakers.
Earlier this year, the House of Representatives passed its version of the bill with an overwhelming majority.
Indian Prime Minister Manmohan Singh strongly defended the deal in the parliament in August.
He said India would not accept any move by Washington that would impede its atomic weapons programme, nor would it allow any international scrutiny of its military facilities.
But Mr Singh also argued that the deal was in India's interests.
He said mass poverty could only be removed by a fast expanding economy, which in turn needed energy.