India and the U.S. are pushing to tie up vital details of a nuclear-energy cooperation agreement approved by their legislatures last year, ahead of Prime Minister Manmohan Singh's visit to the White House Tuesday, said officials from both countries.

India has 17 nuclear-power plants -- including Kakrapar, above, in the western state of Gujarat -- and is building six more to meet growing energy demand.

The nuclear deal was a breakthrough in relations for two nations that were ideologically opposed during the Cold War, and Mr. Singh staked his political reputation to get it approved by a reluctant Indian Parliament.

But American companies haven't yet been able to begin selling their technology and services because of remaining regulatory roadblocks.

"We have made tremendous progress" on the nuclear talks, Timothy Roemer, U.S. ambassador to India, said in New Delhi this week. "We are pushing hard to see a successful conclusion to these issues."

Negotiators from the two nations were due to meet in Washington on Saturday as part of an effort to formalize the pact. The negotiators will focus on an agreement to make sure low-enriched uranium sold by U.S. companies to Indian companies for use in their reactors doesn't end up reprocessed as weapons-grade fuel.

The Obama administration is also seeking greater safeguards for the handling of enriched uranium, and needs a guarantee from India, a nuclear-armed nation, that the fuel won't be used for military purposes, according to officials briefed on the talks.

Washington is also awaiting official assurances from New Delhi -- which refuses to sign the Nuclear Nonproliferation Treaty -- that it won't pass on its nuclear know-how.

Also delaying the conclusion of the nuclear deal is the passage of an Indian law providing U.S. companies with liability protection in the case of nuclear accidents. Companies such as General Electric Co. say the law is a prerequisite for entering the Indian market. India plans a major expansion of nuclear production by 2020 as part of a broader plan to meet rising energy demand.

Senior Indian officials have told U.S. counterparts that they plan to introduce the liability legislation in the coming session of Parliament.

The Obama administration calls its ties with India one of Washington's most important strategic partnerships. U.S. officials said President Obama and Mr. Singh will announce a string of joint projects focused on education, clean energy and defense, following their Tuesday morning meeting at the White House.

On Monday, Mr. Singh will be hosted at a lunch by Vice President Joe Biden and Secretary of State Hillary Clinton. Mr. Obama will host a state dinner for him on Tuesday night.

"We are putting in place now a wide range of bilateral cooperation to really reflect the new level of engagement." Assistant Secretary of State Robert Blake said this week in Washington.

Mr. Singh's visit comes almost a year after gunmen from Pakistan led an assault on Mumbai, India's financial hub, which left at least 170 people dead. The U.S. and India have since stepped up intelligence-sharing and counterterrorism cooperation, and are moving to formalize those arrangements, said Indian and U.S. officials.

Despite growing ties, the U.S. and India are still working through a number of contentious issues, said South Asia experts.

Discussions about the nuclear pact dominated Mr. Singh's trip to Washington in 2005, when former President George W. Bush's administration was pushing aggressively for the deal. Mr. Obama came into office pledging to develop a "regional" solution to South and Central Asia's instability, and specifically cited the need to resolve India's conflict with Pakistan over the Himalayan territory of Kashmir.

The White House initially envisioned its special envoy to Pakistan and Afghanistan, Richard Holbrooke, playing a direct role in mediating the Kashmir issue, according to U.S. officials. But New Delhi pushed backed against any direct American role.

The Obama administration also continues to debate India's growing economic and diplomatic role inside Afghanistan. U.S. officials have publicly praised New Delhi's developmental assistance to Kabul. But privately, officials in Washington say New Delhi's involvement could be driving Pakistan to support the Taliban out of fears of being encircled by India's presence in Afghanistan.

India also remains wary of Washington's regional relationship with China. Indian officials voiced dismay this week after Mr. Obama signed a communiqué with his Chinese counterpart pledging to jointly cooperate to promote stability in South Asia.

New Delhi viewed the statement as the U.S. allowing Beijing to police the countries to its south and west.

"We don't want to be subordinated to China in South Asia," said C. Raja Mohan, an influential Indian strategic analyst, at a Washington policy forum this week.

—Paul Beckett contributed to this article.