* Bonomi could make own bid or up stake to 29.9 pct if Gaillon bid fails-source
* Gaillon's offer secured around 40 pct of Club Med so far - sources
* Paris Court to rule on legal action against Benetton on May 23
* Club Med shares trading at five-year highs (updates with closing share price)
By Dominique Vidalon
PARIS, May 22 Italian businessman Andrea Bonomi may boost his stake in Club Mediterranee to 29.9 percent and does not rule out launching a new bid should the 557 million euros ($761 million) bid he opposes fail, a source close to the situation told Reuters.
The 17.50 euros per share bid launched a year ago by private equity players Ardian of France and China's Fosun International for the French holiday firm is set to close on Friday.
But the share price of Club Med has now climbed well beyond the offer price to trade at five-year-highs above 19 euros amid shareholder opposition to what they consider a low-ball price.
Through his Strategic Holdings fund, Bonomi has built a stake of over 10 percent, becoming Club Med's largest shareholder. He has said he will continue to raise his stake. point.
According to the source, who stressed the scenarios discussed were "hypothetical", Bonomi may take that up to 29.9 percent - the maximum he can hold without launching a full offer - should the Ardian-Fosun bid, made through a vehicle called Gaillon, fail to reach the required 50 percent acceptance.
The source said Bonomi is also considering making his own bid, which would come through one of his funds, Investindustrial. Investindustrial, which owns theme parks Gardaland in Italy and PortAventura in Spain, is considering its options, Strategic Holdings has said.
The source would not provide indications on the price at which a Bonomi offer could be made, but French daily Les Echos has said he considered 21-25 euros a "fair" value.
Club Med shares closed up 0.52 percent at a new 5-year high of 19.20 euros, having gained nearly 10 percent so far this year and 30 percent last year, and leaving analysts betting that the offer will fail.
"It is still hard to know what Fosun/Ardian reaction might be, but we now believe that the current offer will fail," said Kepler Cheuvreux analysts in a note, raising their price target to 20 euros from 17.50 euros to "integrate the higher speculative appeal".
Gaillon Invest, Strategic Holdings and Fosun all declined to comment. Club Med could not be immediately reached for comment.
Gaillon has so far nearly 40 percent acceptances, sources told Reuters. However, at least one shareholder has ducked out of a commitment to accept the offer.
A French court is due to rule on Friday morning on a legal action Gaillon has taken against another Club Med shareholder, the Benetton family, after it removed its backing for the bid and added the weight of its 2 percent stake to those demanding a higher price.
Fosun, with a 9.96 percent stake, and Ardian, with 9.4 percent, have said their plan is to accelerate Club Med's shift to fast-growing emerging markets such as China to counter weak growth in Europe.
"Were the bid to fail, (Club Med) management would be significantly destabilised. Development might suffer especially in China were Fosun to exit at some stage" said Exane BNP Paribas analysts.
French regulators have nine bourse trading days after the close of the offer to release its results. ($1 = 0.7318 Euros)
(Reporting by Geert De Clercq and Dominique Vidalon; Editing by Andrew Callus)