BRUSSELS (Reuters) - European Union antitrust regulators will extend the deadline to May 28 to decide whether to clear Telefonica's (>> Telefonica SA) bid for KPN's (>> KPN KON) E-Plus unit in Germany, the European Commission said on Wednesday, giving the Spanish company more time to submit concessions.

The deal has drawn intense regulatory attention as it would reduce the number of mobile operators from four to three in Europe's biggest market, raising the spectre of higher prices for consumers.

The European Commission cited concerns about reduced competition in the German retail mobile telephony and wholesale access market when it opened an investigation into the deal in December last year.

"The deadline in the Telefónica/E-Plus merger case has been extended by 10 working days in agreement with the parties," said Antoine Colombani, Commission spokesman for competition policy.

Telefonica had been due to present concessions on Wednesday but will now have 10 more working days to do so according to EU merger rules. Telefonica Detuschland (>> Telefonica Deutschland Holding AG) spokesman Albert Fetsch declined to comment.

The mobile operators should give up some radio spectrum to safeguard competition, Germany's telecoms network regulator said on Tuesday.

Rivals Freenet (>> freenet AG) and United Internet have called on the EU watchdog to force Telefonica to give them cost price access to its German network and sell some of its prepaid brands in return for regulatory approval.

(Reporting by Foo Yun Chee; Editing by Elaine Hardcastle)