MANILA, July 2 (Reuters) - Three U.S. private equity companies and Philippine conglomerate San Miguel Corp are among 12 firms that have submitted letters of intent to bid for the government's majority stake in United Coconut Planters Bank, a person with knowledge of the matter said.

CAP IV Engagement Limited, an affiliate of Carlyle Asia Partners IV, Lone Star Funds and TPG Capital Management LP , are interested, while Japan's Mitsubishi UFJ Financial Group Inc (MUFG) is the only foreign bank in the race, said one source, who was not authorised to speak to the media on the matter.

A second source also said that San Miguel had submitted a letter of intent to bid.

Under the terms of the auction, the deal is expected to be worth at least 16.1 billion pesos ($350 million). The government plans to sell its 73.9 percent stake for a minimum of 1.1 billion pesos but has also stipulated that the winning bidder must inject at least 15 billion pesos in capital.

Carlyle Group and TPG declined to comment while Lone Star did not return a Reuters request for comment.

($1 = 45.1350 Philippine pesos) (Reporting by Neil Jerome Morales; Additional reporting by Elzio Barreto in Hong Kong; Editing by Rosemarie Francisco and Edwina Gibbs)