Support from the SP is likely to help the Congress Party-led ruling coalition secure a Parliamentary majority if the Left parties carry out their threat to withdraw support in protest at the nuclear deal.

"The deal is in the interest of the nation, we should have come out in support of the deal a year ago," SP leader Amar Singh told reporters in New Delhi.

Samajwadi Party on Friday hinted that they would back the ruling coalition in Parliament if the communists walked away.

The SP has a history of pragmatic alliances with national parties, but it said that they had buried years of bitter relations and described the Congress party as secular.

"In politics, parties switch sides often, but we never sided with communal forces," Singh said.

He said Congress should seek a vote of confidence in Parliament without any worries. "We will not vote against the Government, even if the communists and other parties do," Singh added.