WASHINGTON - Indian Prime Minister Manmohan Singh said on Monday completing a 2005 U.S.-India nuclear cooperation deal would boost investment opportunities in his country, a hopeful sign for U.S. companies eyeing India's potential $150 billion market in power plants.

Singh, speaking to U.S. business leaders on the eve of talks with U.S. President Barack Obama, said India's ambitious infrastructure build-up would propel growth amid a global slowdown and be open to foreign investors.

We are currently finalizing the details that will make the agreement fully operational, he said of the civilian nuclear deal. This will open a large area of commercial opportunity.

Singh and former U.S. President George W. Bush signed the deal in 2005, but India's parliament has to debate a new law to limit U.S. firms' liability in case of a nuclear accident. The United States has still not signed a nuclear fuel reprocessing agreement with India.

The Indian prime minister did not elaborate on what might be announced at his White House summit on Tuesday regarding the unfinished nuclear deal. But some experts familiar with the talks have said the two leaders might issue a joint statement on implementing a deal that would open India's potential $150 billion market in power plants to U.S. suppliers.

Singh said he and Obama would sign a set of agreements on energy security, clean energy and climate change to deepen cooperation in an economic relationship that has grown rapidly since India began opening its economy 15 years ago.

India's economy was hit by the global crisis and growth moderated to 6.7 percent in 2008 and was likely to grow 6.5 percent this year. But Delhi expects the growth rate to get back to 9.0 percent within three years, Singh told the U.S. Chamber of Commerce in a speech.

He urged the U.S. business community to take advantage of an improved approval and implementation process for infrastructure projects in India and to look at public-private sector projects being signed by his country's federal and state governments.

We need massive investment in energy, transport and urban infrastructure to be able to support a high rate of economic growth, Singh said.

Two-way trade, was just $5 billion in 1990 and $14 billion in 2000. But commerce rose to nearly $50 billion last year, according to U.S. figures, making the United States India's largest trading partner.

Indian Ambassador Meera Shankar told a separate gathering of businessmen that India-U.S. trade had doubled in the three years before the global financial crisis erupted last year and that U.S. exports had tripled during that period.

(Editing by Cynthia Osterman)