"There is some delay but we have not reached the end of the road," Singh told a joint news conference with visiting German Chancellor Angela Merkel in New Delhi.

Left parties have threatened to withdraw support for Singh's ruling coalition if the nuclear deal went ahead, which could lead to the fall of the Congress-led government.

Earlier, US Treasury Secretary Henry Paulson had said in New Delhi that Indian approval of the nuclear energy deal with the United States would be seen positively by global business,

"I believe it would be perceived positively by the global business community if it goes through," Paulson told journalists accompanying him on his four-day visit to India.

He would not be drawn on whether business would view it negatively if the deal did not go ahead.

Earlier in the day, Paulson said Washington valued the fact that India was a vibrant democracy and said democratic processes needed to work for the country to come to a conclusion on the nuclear deal.

"Let's let the process in India work on the civilian nuclear deal," Paulson told a business conference.

Last week, Paulson said growing ties between the United States and India were broader and deeper than any single transaction.

India has set itself a target of producing 20,000 megawatts (MW) of nuclear power by 2020, but the country's atomic energy department chief said on Tuesday it would fall short of the goal by 6,000 MW if the deal failed.

Supporters of the deal hope that it would give India much-needed uranium to power its reactors and eventually lower dependency on coal, which accounts for nearly 41 percent of its energy needs and has become a focus of global worries over climate change.

Critics of the deal say nuclear energy will remain a small part of India's power supply for the next 25 years even if the pact materialises, and coal will remain vital.