"They will have to do it without us," party General Secretary A B Bardhan said when asked what the Left would do if the government ignored their objections and went ahead on the deal.
Asked whether the Left would move a no-confidence motion against the government in that case, he said: "it means nothing of that sort".
To another question whether the Left would go with BJP if they moved such a motion, he said, "we generally don't" go with the saffron party. However, Bardhan added "if that happens, we will see at that time".
The veteran communist leader said this in an interview on Karan Thapar's "India Tonight" programme on CNBC TV18.
He said the outside supporters would take a "hard" stand against the government on the nuclear deal as well as major issues like price rise and the agrarian crisis. "It will be a hard decision".
However, he added that "you are forgetting that we are nine months away from elections. I don't see which political party will move a no-confidence motion when elections are just nine months away."
Bardhan's statement came a week ahead of the four Left parties' meeting, which is likely to review the overall political situation and the government's "failure" on various fronts including price rise and the nuclear deal.
