NEW DELHI: The US ambassador to India said Wednesday he hoped a landmark deal on nuclear energy cooperation with the United States could be sent to Congress for approval in September, one day after India’s government won a confidence vote that paves the way for the agreement to move forward.

Prime Minister Manmohan Singh was forced to call the confidence vote after communist political parties withdrew their support for his government this month to protest the agreement, fearing it would draw India closer to the US.

On Wednesday, several key Indian political parties, including the communists, said they were forming an alliance to oppose the government.

Though Singh made enemies in his bid to push ahead with the nuclear deal, he had the backing of India’s powerful business community. Markets surged on Wednesday as business leaders and investors anticipated a slew of economic changes that had been stalled because of the government’s now-defunct alliance with the communists.

The nuclear pact would end more than three decades of nuclear isolation for India, opening its civilian reactors to international inspections in exchange for the nuclear fuel and technology it has been denied because of its refusal to sign the Nuclear Non-proliferation Treaty and its testing of atomic weapons.

India imports about 75 per cent of its oil, and Singh has argued the country needs the nuclear deal to power its financial growth and lift hundreds of millions of its 1.1 billion citizens out of poverty.

To finalise the deal, India must strike separate agreements with the International Atomic Energy Agency as well as the Nuclear Suppliers Group of countries that export nuclear material. Then the US Congress will need to approve the accord.

US Ambassador David Mulford said Washington hoped New Delhi would quickly finalise the deal so it could be presented to Congress for approval in early September.

“We are delighted that this has taken place and we are organising ourselves and stand ready to move ahead with the final steps of the civil nuclear initiative,’’ Mulford told reporters.

The new political alliance brings together the government’s former communist allies, a rising regional party and several smaller groups. It said despite the vote of confidence, the government had been irreparably tainted by accusations of corruption and vote buying in the run up to the confidence vote.

Leaders of the new alliance did not immediately outline the steps they planned to take to oppose the government.

At a meeting of the alliance on Wednesday, Mayawati, India’s most powerful low-caste politician who goes by just one name, accused the government of “murdering democracy.’’

Singh and his Congress party had fought hard to secure their victory in the confidence vote, and appeared to cut back-room deals when all else failed. An airport was named after one lawmaker’s father, another was promised a high-level job and – rival politicians allege - many others received millions of dollars in bribes.

At one point, legislators from the Hindu-nationalist Bharatiya Janata Party pulled large bundles of cash out of bags they said contained tens of millions of rupees, alleging Congress and its allies had tried to bribe them to abstain.

Authorities have promised an investigation into the charges.

With the communists out of the way, Finance Minister Palaniappan Chidambaram said the government would press ahead with long-stalled plans that could include loosening India’s restrictive labour laws and further opening its financial sectors.

However, Tushar Poddar, an analyst at Goldman Sachs, noted the government has only 10 months to go before the end of its term. He said it would be hampered by its fear of alienating voters who are already contending with sharply rising food and fuel prices. “Sweeping reforms are not on the agenda,’’ Poddar said.