NEW DELHI: India's parliament will hold a confidence vote Tuesday to decide the fate of an embattled coalition government and its controversial nuclear energy deal with the United States.

After weeks of intensive horse-trading and a day of stormy debate pitting the Congress-led government of Prime Minister Manmohan Singh against left-wingers and Hindu nationalists, the outcome is seen as too close to call.

Projections by Indian news channels showed the opposing sides to be running almost neck and neck, with the government perhaps a whisker ahead by one or two votes in the 543-seat house.

Singh needs a simple majority to survive and see through the last year of his mandate. If he fails, the world's largest democracy will be headed into early elections, most likely after the monsoon season ends in late September.

"It is a tight race, no doubt about that," analyst and opinion pollster Yashwant Deshmukh told AFP late Monday.

Still, he said the government could just pull through: "The government would never have gone for the vote if they were not sure of winning."

The prime minister also exuded confidence on the floor of the house on Monday, and Congress on Tuesday will bring out its elegant and charismatic leader, Italian-born widow Sonia Gandhi, in a final bid to win over undecided deputies.

The vote was triggered after a bloc of left-wing and communist parties pulled their support for Singh in protest over the deal with Washington designed to bring India into the global loop of nuclear commerce after decades of isolation.

The nuclear deal allows India, which has nuclear weapons and refuses to sign the Non-Proliferation Treaty, to be treated as a special case on condition it separates its civil and military programmes and allows some UN inspections.

Government officials gave an impassioned defence of the deal during Monday's debate, arguing that the country's 1.1 billion people badly needed alternative sources of energy to avert an impending fuel crunch.

India's power stations cannot keep up with demand, coal is running out, and power cuts are frequent - not the recipe for continued strong growth of nine percent plus, the government has argued.

But left-wingers and the main opposition Hindu nationalist Bharatiya Janata Party (BJP) say the deal ties traditionally neutral India too closely with the United States, and would compromise the country's nuclear weapons programme.

They are equally confident they can win and bring down the government.

The race is so tight that the government has let six MPs serving jail terms out of prison to vote.

The opposition has also paid for special planes to bring in lawmakers who were in hospital - although BJP leader Lal Krishna Advani insisted it was the government that was "like a patient in an intensive care unit."

The communists have also been trying to widen the terms of the debate - speaking out against rising food and fuel prices, and arguing that hundreds of millions of poor have been left behind in India's economic boom.

Voting is expected to take place late Tuesday following a second day of speeches in the house, including presentations by Sonia Gandhi and her son and heir apparent, Rahul.

- AFP/yb