“The party will not allow the UPA government to proceed with the pact to help US President George W Bush when elections are round the corner in America,” Achuthanandan said.

India is in the midst of negotiations with the IAEA to firm up a safeguards agreement before approaching the 45-member Nuclear Suppliers Group (NSG) for changes in its guidelines to permit international nuclear commerce.

“We will not hesitate to withdraw support to UPA if they choose to go ahead with the deal,” he said.

Achuthannandan’s remarks come within days of CPI-M patriarch Jyoti Basu and party General Secretary Prakash Karat clarifying that while they stoutly opposed the nuclear deal, there was no threat to the UPA government.

Their clarification had come after CPI-M leaders had issued veiled threats saying there would be “serious consequences” if the government went ahead with the deal.

The UPA-Left committee on the nuclear deal is likely to meet before the budget session of Parliament to take stock of the negotiations at the IAEA.