LONDON/MADRID (Reuters) - Ck Hutchison Holdings (>> CK Hutchison Holdings Ltd) will not offer EU regulators further concessions to secure a takeover of Telefonica's (>> Telefonica SA) O2 and is ready to challenge a rejection of its bid, sources familiar with the matter said.

The Hong-Kong-based group still hopes to persuade the European Commission to allow its 10.3 billion pound bid to become Britain's biggest mobile operator, which will cut the number of players from four to three. But although talks with Brussels are still going on, Hutchison, controlled by Asia's richest man, Li Ka-shing, will not offer any more concessions, two sources told Reuters.

"Hutchison has gone out of its way to offer substantial remedies for the O2 deal. It will fight in court if EU regulators want to block the deal," one of the sources said.

The proposed combination could pave the way for consolidation in other European markets, including Italy where Hutchison and Vimpelcom agreed last year to merge their mobile units.

However, Britain's competition watchdog and telecoms regulator both oppose the deal, and their views may carry extra weight when a debate is raging in the country about the power wielded by Brussels ahead of a vote on EU membership in June.

The EU antitrust watchdog is likely to decide on the deal in the coming weeks, with a formal decision expected by May 19.

O2's owner Telefonica is increasingly worried it will have to abandon the deal, which values Britain's second largest mobile firm at about 7.5 times earnings before interest, tax, depreciation and amortisation (EBITDA).

That is a price that private equity firms would not be able to afford, sources familiar with the matter said.

Hutchison and Telefonica both declined to comment on Wednesday, while a European Commission spokesman could not immediately be reached for comment

TELEFONICA'S PLAN B

Telefonica, which bought O2's assets in Britain, Germany and Ireland in 2005, is working on a contingency plan to cut debt and appease ratings agencies in case the deal with Hutchison falls through, one of the sources said.

The source said a wide range of options were being looked at, but a fire sale of O2 or a dividend cut were off the table, although Telefonica would stick to a complementary dividend paid in shares and would not start paying it in cash as flagged.

The contingency plan is designed to provide enough breathing space for Telefonica to review other strategic options for O2, which as well as a sale could also include merging it with another UK player such as Sky or TalkTalk (>> Talktalk Telecom Group PLC).

The proposed deal between Hutchison and Telefonica has led British regulators to voice concerns with the UK's Competition and Markets Authority (CMA) and a call for the European Commission to prevent "long-term damage" to the UK mobile telecoms market.

The CMA Chief Executive Alex Chisholm said last week that a merger was likely to lead to increased prices and/or a reduction in quality for UK consumers. But for Hutchison, it offers a unique opportunity to expand its European footprint and gain access to O2's 22 million subscribers, after consolidating the German and Irish markets.

Hutchison is prepared to challenge any EU veto in court, one of the sources said, and a block to the deal could even prompt the diversified conglomerate to get out of British telecoms, where it already owns the Three network.

An EU veto was also likely to colour Hutchison's future negotiations with European regulators, making it reluctant to negotiate remedies for a long-awaited mobile deal in Italy, one of the sources said.

Opposition to a planned merger in Denmark between TeliaSonera and Telenor led them to abandon their plans last year, raising concerns that larger mobile telecom deals might also run into trouble.

Another rejection would signal that EU Competition Commissioner Margrethe Vestager is taking a harder line than predecessor Joaquin Almunia, who had approved similar mobile consolidation deals in Austria, Ireland and Germany.

(Additional reporting by Paul Sandle; Editing by Alexander Smith)

By Pamela Barbaglia, Julien Toyer and Andrés González