A joint panel formed to try and end the face-off will make a fresh attempt to convince communist leaders who have threatened to end their support to Prime Minister Manmohan Singh's coalition if it pursues the historic pact.

Two meetings of the panel, formed in August when the crisis erupted, have produced little to achieve a breakthrough and few are betting on the third round to help break a deadlock that is threatening to trigger early elections. "At this point of time, we are neither optimistic nor pessimistic," Hannan Mollah, a senior left leader, said ahead of the meeting.

"We have explained our views, we have clearly told them this far and no further," he said. "Now everything depends on the government. It is now up to them whether they want to survive or whether they want to go."

The civilian nuclear cooperation deal is seen as a major milestone in the new strategic partnership between India and the United States, not the best of friends during the Cold War.

If and when approved, it will allow India to import US nuclear fuel and reactors, despite having tested nuclear weapons and not signing the Non-Proliferation Treaty.

But communist parties, who shore up Singh's coalition, have opposed the deal, saying it undermines India's independent foreign policy and draws New Delhi into a strategic alliance with Washington.

Friday's meeting is considered crucial as India faces an informal end-October deadline to start work on securing the remaining approvals to clinch the deal before Washington gets preoccupied with presidential elections next year.

The government and the ruling Congress party have remained steadfast on pushing the deal, and failure to make any progress on Friday could indicate the end of the road for their relationship with the left parties, analysts say.

While the Congress has put a brave face on the deal, it has also started preparing for early elections, shuffling party leaders and announcing a slew of populist welfare measures to woo poor voters.