New Delhi - Communist allies of India's United Progressive Alliance Wednesday formally withdrew their support to the ruling coalition over a civilian nuclear deal with the US and demanded a trust vote in the Indian parliament.

Leaders of the four left parties that have provided the Congress-party led UPA with its parliamentary majority since May 2004 met President Pratibha Patil to hand over letters of withdrawal of support.

"We have met the president and all four of our left parties have submitted letters withdrawing support from the UPA government," Prakash Karat, general secretary of the Communist Party of India (Marxist), told reporters in the forecourt of the Presidential Palace after meeting Patil.

"We have also submitted a second letter requesting the president to convene a session of the Lok Sabha (lower house of Indian parliament) and direct the prime minister to seek a vote of confidence," he added.

The communist parties had announced the move to quit the UPA on Tuesday soon after Prime Minister Manmohan Singh's statement that the government would approach the International Atomic Energy Agency for a safeguards pact to implement the nuclear agreement.

"As you are aware the left parties had warned that they would withdraw support if the UPA took the next step to operationalize the nuclear deal," Karat said, charging the Singh government of not being transparent on the agreement.

The communists oppose the nuclear deal, saying it would compromise on India's strategic sovereignty and make the country a "stooge of US imperialism."

The leftist combine includes the CPI-M, Communist Party of India (CPI), Revolutionary Socialist Party and the Forward Bloc and have 59 members in the 543-member Indian lower house of parliament.

However, the leading Congress party claims that it has the numbers for a majority in the parliament in case a no-confidence motion was called.

The UPA government, whose five-year term ends in May 2009, has ruled out early elections, saying it has the support of the Samajwadi (Socialist) Party that has 39 members as well as other smaller political parties in the parliament. (dpa)