Indian and U.S. officials have begun talks in New Delhi to work out the final details of a landmark civilian nuclear energy deal.

Before Thursday's meeting with India's Foreign Minister Shiv Shankar Menon, U.S. Undersecretary of State Nicholas Burns said the two sides have made a lot of progress, but that hard work remains.

Neither Burns nor Indian officials have said what issues must be settled in the two days of talks.  But, India has objected to conditions that would allow Washington to stop nuclear cooperation if New Delhi conducts another nuclear test.

India is also against proposed U.S. restrictions on its ability to reprocess spent nuclear fuel.  Reprocessing is a key step in making weapons-grade nuclear material.

The deal would reverse three decades of U.S. sanctions on nuclear trade with India, which has not signed the nuclear Non-Proliferation Treaty.

A preliminary agreement was signed during President Bush's visit to India in 2005 and approved by U.S. Congress last December. 

Under the proposal, the U.S. said it would ship nuclear fuel and technology to India in return for India accepting U.N. inspections of its 14 civilian nuclear plants.

Critics of the proposed deal fear it could enable India to boost its nuclear weapons program and lead to a nuclear arms race in Asia.

Both India and neighboring Pakistan possess nuclear weapons technology, which was confirmed by the detonation of a series of nuclear devices by the two countries in 1998.

Some information for this report was provided by AFP and Reuters.