* Bid gives Vivendi 10.5 bln euros in cash
* Rival Numericable bid offers 11 bln in cash
* Bouygues would spin off new entity after acquisition
PARIS, March 6 (Reuters) - Bouygues on Thursday made an offer for larger telecom rival SFR, which promises a bigger potential payday for seller Vivendi than a competing offer from Numericable but has more regulatory risks.
French telecoms and construction group Bouygues has offered Vivendi 10.5 billion euro in cash and 46 percent of the new company after a planned spin off, valuing SFR at 14.5 billion euros before benefits from the deal and 19 billion after these are taken into account.
Cable operator Numericable has made a bid that included 11 billion euros ($15.11 billion) in cash, granting Vivendi a 32 percent stake in the new company, sources said earlier.
A SFR-Bouygues tie-up would create Europe's seventh biggest telecom group in terms of sales and in France it would rank ahead of current French leader Orange in market share.
If accepted by Vivendi and approved by regulators, it would consolidate the French market from four to three mobile players that could end a price war sparked by low-cost operator Iliad's entry into the mobile arena in January 2012.
The price war is partly why Vivendi has been seeking to cut its exposure to capital-intensive telecoms business to focus more on its media business, such as pay-television and music. It was preparing to split SFR into a separately listed company this summer, but is also open to offers for the business.
The outcome of the bidding war for SFR will depend largely on how Vivendi's board gauges the value of the shares it will get in the new telecom group, as well as potential cost savings, people close to the deal said. Vivendi is expected to review the offers in the coming weeks.
Bouygues, founded by billionaire Martin Bouygues, potentially has the tougher battle to win SFR because merging the number two and three mobile operators in France would attract intense regulatory scrutiny.
Numericable would not face such obstacles because it is not a force in mobile. It owns a cable network to two-thirds of French households and sells broadband and television services.
Bouygues Chief Financial Officer Philippe Marien said no talks had yet begun with French antitrust regulators but that the group was ready to take steps to protect competition.
"We will do what it takes for the market to stay competitive," he said.
Sources said earlier Bouygues would be ready to sell mobile spectrum and some of its 15,000 mobile antennas. Iliad, which has been racing to build out its mobile network, would be the obvious buyer and beneficiary of such disposals, analysts said.
Marien said Bouygues would also help virtual mobile operators, which rent capacity on other carriers' networks, to preserve competition. Similar measures helped to get telecom deals approved in Austria.
Bouygues did not say whether the offer to Vivendi included a break-up fee to cover the regulatory risk.
The Bouygues deal would merge SFR into Bouygues and then split out the combined telecom company into a listed entity.
Bouygues would remain the largest shareholder with 49 percent, Vivendi with 46 percent, and outdoor advertising group JCDecaux, a long-time investor in Bouygues Telecom, would own the remaining 5 percent.
As part of the spin-off, the new telecom company would carry out a capital increase that Bouygues would not subscribe to. Marien said 3 billion euros would be raised from the share sale and asset disposals expected to placate antitrust regulators.
Once listed, Vivendi would be allowed to sell off a further 15 percent stake in the new company, Bouygues said, allowing it to progressively exit telecoms, Vivendi's original aim of putting SFR on the bloc. "Vivendi will then be free to sell its remaining interest when it sees fit to do so," Bouygues said.
One key question for Vivendi is which of the deals will deliver the most cost savings, which would eventually boost the value of the shares that Vivendi will receive.
Bouygues estimated the net present value of the cost savings from the deal would be 10 billion euros, with 80 percent coming from operational costs and 20 percent from network investments.
Numericable has not publicly given a comparable figure. Media reports have put it at 6 billion euros. A source close to the company said benefits could be up to 12 billion euros.
Analysts earlier put cost savings at around 4 billion euros. Barclays analysts said the Bouygues deal is likely to generate double the synergies of Numericable's offer.
Shares in Bouygues were up 7.5 percent at 30.93 euros by 1124 GMT, while Numericable shares were down 7.5 percent at 28.80 euros. Vivendi's stock was up 2 percent before paring gains. It was up 1 percent at 20.80 euros.
Bouygues was advised by HSBC and Rothschild on its bid. HSBC is financing the debt for the offer.