Communist leaders Prakash Karat and D Raja were on Sunday set to meet Tamil Nadu Chief Minister M Karunanidhi over the India-US nuclear deal stalemate that is threatening the future of Prime Minister Manmohan Singh's government.

Both Karat, general secretary of the Communist Party of India-Marxist (CPI-M), and Communist Party of India (CPI) national secretary Raja have reached Chennai. It is not clear if they will meet Karunanidhi together.

"I am meeting the DMK leader to apprise him of our stand on the issue," said Raja.

Karunanidhi, whose party has had close ties with both the CPI and CPI-M for decades, declared on Saturday evening, "We have a duty to resolve the differences between the Congress and Left parties on the issue in the interest of the nation to find an amicable solution."

The CPI and CPI-M along with the Revolutionary Socialist Party (RSP) and Forward Bloc are adamant that the Manmohan Singh government should not go ahead with the civil nuclear deal.

They have rejected the government's plea to give it the green signal for finalising the India-specific safeguards agreement with the International Atomic Energy Agency (IAEA) - a crucial step to take the deal ahead.

The CPI-M has warned it would review its ties with the government if the latter approached the IAEA. The four Left parties provide crucial legislative backing to the Congress-led government in which the DMK is a major partner.