Prakash Karat, leader of the Communist Party of India (Marxist), said that he would be open to talking to the Congress party to help support the formation of an alternative national government after a general election.
"We can do business with them and ask them to support an alternative secular formation, it's possible- why not, I don't rule it out," Karat said in an interview with NDTV news channel.
The CPI(M) is a major force behind a "Third Front" of smaller regional parties that aims to challenge India's two main national alliances led by Congress and the Bharatiya Janata Party.
The communists quit their support for the ruling Congress-led coalition last year over opposition to a civilian nuclear deal with the United States.
"It's not a question of untouchability. We'll do business with all parties but that business will be circumscribed by the nature of the mandate," Karat said.
Karat's statement signals that despite a bitter war of words between the left parties and Congress over that nuclear deal, they could once again try and form a government.
The CPI(M) was the biggest of several left parties that backed the Congress government for four years after the last 2004 general election, blocking many economic reforms.
The full interview will be broadcast on Sunday.