India's Foreign Minister Pranab Mukherjee has virtually ruled out signing a controversial nuclear deal with the United States without the support of its communist allies, sparking fresh uncertainty about the fate of the pact.
The communists oppose what they see as a strategic alliance with the US, and have threatened to withdraw vital support from the ruling coalition if it moves ahead with the deal.
A voter-friendly budget presented last month fed talk that the Congress party-led government was preparing to dump its leftist allies, sign the deal and face early elections.
But Mukherjee has rejected such a possibility, saying it would not be possible to sign a major international deal as a minority government, if the Left pulled out.
"A minority government cannot, need not and should not sign a major agreement like this," Mukherjee told the Outlook magazine, adding even Washington would not agree to it.
The Indian government has said it is seeking the broadest possible political consensus over the deal which Washington says should be concluded before the Nov 4 US election. The deal will give India access to American nuclear fuel and technology.
"First the consensus will be with the supporting parties," Mukherjee said. "Then we shall try to evolve a larger consensus.
"If the government does not exist, how can there be an agreement? So we shall have to carry them (leftists) along."
Mukherjee's comments came after the Communist Party of India-Marxist (CPI-M) hardened its stance and gave the government until March 15 to convene a meeting to discuss the status of the deal.
The communists had allowed the government to negotiate global approval for the deal with the International Atomic Energy Agency (IAEA), but have indicated they will be looking for a firm commitment at that meeting not to "operationalise" the deal.
"If the government thinks that after arriving at an agreed text with the IAEA they can proceed to take the next steps for operationalising the agreement, they are mistaken," an article in a CPI-M mouthpiece, People's Democracy, said.
"The future of this government depends on the decision they will take."
Congress needs the support of the communists to get its budget through parliament, with a vote likely in early May.
For the time being, keeping its coalition together could be the main priority, even if that means promising not to advance the nuclear deal, analysts said.
The deal, to become effective, has to be ratified by the 45-member Nuclear Suppliers Group after clearing the IAEA and placed before the US Congress for a final approval.
Washington has said time is tight and a short US legislative calendar ahead of the American presidential election could complicate the deal's passage.