NEW DELHI – The Indian government's bid to secure political support for a civilian nuclear deal with the United States stalled Thursday when a key regional party asked for more time to make a decision.

Prime Minister Manmohan Singh has been wooing the Socialist Party because its backing would offset the potential loss of communist allies who have threatened to withdraw their support in India's Parliament for the ruling coalition if Singh moves ahead with the nuclear deal.

The communist parties are not part of the ruling coalition, which is led by Singh's Congress Party, but their support is crucial to its stability. Without that support, the government could topple and face an early election later this year.

Mulayam Singh, the Socialist Party chief, held talks Thursday with his supporters and told reporters that he “needs to consult nuclear scientists before making a final decision.”

The government assured Singh's party on Wednesday that there was nothing in the agreement with the U.S. that would place an embargo on India's right to carry out a nuclear test or affect India's decision-making in foreign policy, according to a news release by the prime minister's office.

Meanwhile, Democratic Rep. Gary Ackerman, chairman of the House of Representatives Foreign Affairs Subcommittee on South Asia, told Indian leaders they needed to sign the deal soon or risk losing the opportunity.

“The calendar is running quickly,” Ackerman said, according the Press Trust of India news agency.

On Thursday, a Congressional delegation, led by Ackerman, met Shyam Saran, the prime minister's special envoy on the nuclear deal, and Shivshankar Menon, India's top bureaucrat in the foreign ministry.

Indian communist party leaders oppose the deal because they argue it would give the U.S. too much influence over their country's foreign policy and would undermine India's weapons program, and ultimately threaten national sovereignty.

An agreement with Washington would reverse three decades of U.S. policy by allowing the shipment of atomic fuel and technology to India, which has not signed international nonproliferation accords but has tested nuclear weapons. India, in exchange, would open its civilian reactors to international inspections.

The deal has been hailed as the cornerstone of a new strategic relationship between the U.S. and India.

For India to move ahead with the deal it needs to sign a separate deal with the U.N.'s International Atomic Energy Agency before the U.S. Congress can approve the pact.