DELHI, India — The future of India’s government and a crucial deal with America on nuclear technology hung in the balance yesterday as parliament began debating a confidence motion.

Manmohan Singh, the prime minister, called the vote in a last-ditch attempt to win approval for a nuclear agreement, which Left-wing allies of his coalition have bitterly opposed.

Under the deal, America would give India civilian nuclear technology in return for the country’s adherence to safeguards preventing the spread of the means to build atomic weapons.

Mr. Singh believes this deal is crucial to India’s future as a rising power. The economy has grown by 9% for the last three years — but the boom can only continue if chronic electricity shortages are overcome. India needs to increase the amount generated by civil nuclear power stations fivefold in the next 10 years, according to the government.

The deal would lift all restrictions on the transfer of civil nuclear technology and provide American technical help

“We will prove our majority on the floor of the house,” Mr. Singh said as he opened the debate. “I have no doubt that the people of India, when they consider what we have done, will reaffirm their confidence in us.” Of the 543 members of the Lower House, the Lok Sabha, the government needs 271 to win the debate, avoid fresh elections and carry the nuclear deal. The vote, which is expected today, will be very close.