By Bappa Majumdar

NEW DELHI, July 5 (Reuters) - A key regional party in India said on Saturday it backed the government over a controversial nuclear energy agreement with the United States, easing concerns the pact could trigger early elections.

Support from the Samajwadi Party (SP) is likely to help the Congress Party-led ruling coalition secure a parliamentary majority if communist 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.

The regional party from Uttar Pradesh state had 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.

With time fast running out, the government needs to seek approval for the deal from the International Atomic Energy Agency (IAEA), the next international move needed to make the agreement operational.

The left says the pact will make India a pawn of Washington, while critics argue their strident opposition is more due to an ideological dislike of the United States.

The pact, which would give India access to U.S. nuclear fuel and technology, is potentially worth billions of dollars to U.S. and European nuclear supplier companies and would give India more energy alternatives to drive its development.

Analysts say it would shift trade and diplomatic ties towards the West. (Editing by Jeremy Laurence)

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