The exercise to resolve the current stand-off over the nuclear deal began on Monday evening with senior Congress leaders holding talks with their Communist Party of India counterparts who have taken an aggressive stance against the agreement.

External Affairs Minister Pranab Mukherjee, Defence Minister A K Antony and political secretary to Congress president Ahmed Patel were closetted with CPI general secretary A B Bardhan and party leaders D Raja and Gurudas Dasgupta.

This is the first formal interaction between a group of the Left party leaders since the Left threat of serious consequences if the 123 agreement was operationalised.

Bardhan recently made it clear that the Left parties were not prepared to back down on their demand and said it was for the government to decide whether it should continue or to commit "sati".

"It has to take a decision on the nuclear deal. If the government is bent on falling then who can stop it," he had said.

The government is expected to hold talks with the CPI-M leaders later.