Stepping up pressure on the United Progressive Alliance government on the foreign policy front, Communist Party of India-Marxist virtually warned it against 'compromising on vital issues' to clinch a deal to operationalise the Indo-US civil nuclear deal.

The party and its Left ally Communist Party of India also flayed the decision to allow a nuclear-powered US aircraft carrier, which was part of 'hostile operations against Iraq' to make a port call at Chennai.

CPI-M general secretary Prakash Karat said: "It was still not clear what the agreement being arrived at by India and the US is about as negotiations progress to narrow down differences on the 123 agreement to operationalise the deal."

"The UPA government should not try to clinch an agreement by compromising on vital issues raised by Hyde Act or by trying to avoid such issues in the 123 bilateral agreement," the party said after its Central Committee met in New Delhi over the last three days.

"The Hyde Act cannot be the basis for bilateral agreement on the civil nuclear deal with the US," Karat said, referring to the act passed by the US Congress setting the terms and conditions for the nuclear deal.