The agreement, which took two years to complete, spells out how a plan for Washington to share nuclear technology with New Delhi will work, including thorny issues like reprocessing rights and a fuel reserve for India.

"The United States will support an Indian effort to develop a strategic reserve of nuclear fuel to guard against any disruption of supply over the lifetime of India's reactors," the text says.

India's main opposition dismissed the Indo-US nuclear deal yesterday as "unsatisfactory" but atomic scientists gave it the thumbs up, saying the country's strategic interests had been safeguarded.

The communists, key allies of the ruling Congress party, said they wanted time to study the landmark civilian nuclear agreement before reacting.

Key defence scientist K Santhanam said the deal was "historic" paving the way for India to meet its energy demands.

But JP Mathur, senior leader of the Hindu nationalist Bharatiya Janata Party (BJP), whose last government staged nuclear tests in 1998, told AFP: "It is an unsatisfactory deal.

"Washington could pull out of the deal if India tested a nuclear device."

Former BJP foreign minister Yashwant Sinha said Washington had offered no firm commitment to New Delhi regarding fuel supply, reprocessing and return of equipment as part of the nuclear deal.

"There are a lot of unenforceable commitments from the US in lieu of enforceable commitments from India," he said.

The deal, clinched in Washington last month, wrapped up two years of negotiations and aims to bring New Delhi into the loop of global nuclear commerce after a gap of three decades.