UPDATE 3-Indian PM calls for vote of confidence

(Adds details, U.S. statement)

By Alistair Scrutton

NEW DELHI, July 10 (Reuters) - Indian Prime Minister Manmohan Singh on Thursday sought a vote of confidence in his government after his communist allies withdrew their support in protest against a nuclear deal with the United States.

The date of the parliamentary vote will be announced on Friday. Singh met President Pratibha Patil after the government's former communist allies had demanded the vote.

"Dr. Manmohan Singh called on the president today," said a statement from the president's office. "He stated that he and his cabinet colleagues are keen to seek a vote of confidence as early as possible."

Singh's four-year-old government has secured the backing of the regional Samajwadi Party, but it is unclear if the ruling coalition has enough votes for a parliamentary majority.

A defeat for the government in a confidence vote would trigger an early election, probably destroying chances of the nuclear pact going ahead and sparking political uncertainty as the country struggles with record inflation and rising interest rates.

The government needs several votes from other smaller parties and must hope there is no rebellion within the ranks of the Samajwadi Party against the nuclear deal, which critics say gives the United States too much influence over India.

India's 543-member house includes scores of small parties from dozens of ethnic groups and castes, making it unclear whether the government has the necessary support.