UPDATE 2-Bulgaria to open tender for 4th mobile operator

(Adds details, Turkcell comment, paragraphs 4-6)

SOFIA, June 3 (Reuters) - Bulgaria will hold a tender for a fourth mobile phone licence most likely at the end of July, the telecoms regulator said on Tuesday.

Some 12 companies, including Turkish mobile operator Turkcell TCELL.IS, are expected to bid at the tender, which will have a starting price at 38 million levs ($30.33 million), the regulator's spokeswoman said.

"We have decided to launch a closed tender for limited free frequencies with a national-wide coverage for GSM services," the spokeswoman said.

The Communications Regulation Commission said it would publish the tender details by June 10 and invite all interested companies to buy tender documents for the 20-year long licence.

Turkcell confirmed it had sent a letter of interest for the licence but said it has yet to decide whether or not to bid.

"After we study the tender documents we will decide whether or not we will participate ... The company has made no decision yet," Turkcell Deputy General Manager Koray Ozturkler told Reuters.

The three current mobile phone operators in the Balkan country of 7.7 million people, have so far not expressed interest in the tender, although initially Telekom Austria's (TELA.VI: Quote, Profile, Research, Stock Buzz) Mobiltel and Cosmote's COSr.AT Globul considered it.

Bulgaria's third GSM operator, Vivatel, part of telecoms BTC BTCC.BB and owned by U.S. insurance giant AIG (AIG.N: Quote, Profile, Research, Stock Buzz) has also said it was not interested.

Penetration of mobile services in the European Union newcomer exceeds 130 percent, recent data showed. (Additional reporting by Ercan Ersoy in Istanbul) (Reporting by Tsvetelia Ilieva; Editing by Elaine Hardcastle)