* CEO Juan Bejar to leave post before year-end
* FCC needs fresh strategy to shave debt and grow
* May make new rights issue to cut debt costs (Adds financial details, quotes, shares)
By Carlos Ruano and Robert Hetz
MADRID, July 10 (Reuters) - Spanish builder FCC's CEO Juan Bejar has told the firm he plans to leave before the end of the year, a source familiar with the matter said, a move that would see top shareholder Mexican tycoon Carlos Slim tightening his grip on the company.
The departure of Bejar, a well-known executive in the industry who was appointed in 2013, could take place after summer and would pave the way for another potential rights issue as well as a strategy change, the source also said.
FCC declined to comment.
The construction and services firm is struggling to boost profitability and cut a costly debt pile, even after Slim took a 25 percent stake when he bought the lion's share of a 1 billion euro ($1.1 billion) rights issue in December last year.
FCC is one of the worst performers on Spain's blue chip index and has lost a quarter of its stock value since the December rights issue, with uncertainty over Bejar's intentions since the arrival of Slim hanging over its shares.
Sources said Bejar, whose contract includes an around 10 million euro severance payment if control of the builder changed hands, was ready to step down last December but creditor banks insisted he should stay a while longer.
On Friday, FCC shares gained 1.3 percent to 8.956 euros each, underperforming a 2.12 percent rise on the Spanish index .
"The market is now expecting Bejar's departure and until that happens it seems hard to make serious strategic decisions," the source said.
Slim cannot own more than 30 percent of FCC without launching a full takeover bid. If the company wants to raise fresh cash, it will have to convince its other shareholders, including U.S. billionaire Bill Gates, that there is a turn-around strategy for its construction and real estate business.
With 5 billion euros of debt and a debt to EBITDA ratio of 6.2 times at the end of 2014, the company has pledged to reduce borrowings below 4 times EBITDA (earnings before interest, taxes, deprecation and amortisation).
But analysts said this would require shaving 1.5 billion euros off its debt or boosting EBITDA by 50 percent, both difficult tasks in a weak Spanish construction sector that has triggered seven years of declining revenues for the builder.
A debt refinancing plan would put the company in a better financial position to expand in higher growth markets in Latin America, particularly with the help of Slim, who is ranked by Forbes as the world's second richest man, they also said.
Options include a bond issue or even a fresh rights issue, which sources said creditor banks have proposed as a condition to refinance debt again and reduce high debt costs.
Under a hypothetical 500 million euro rights issue, Slim would have to pay 125 million euros to retain his stake, while the financially-stretched founding Koplowitz family would likely see its holding reduced to 17 percent from 22.5 percent.
Slim made a big bet on the European telecoms market in 2012, with purchases of stakes in Telekom Austria and Dutch group KPN, but his track record in that sector so far has been mixed. ($1 = 0.9083 euros) (Reporting by Carlos Ruano and Robert Hetz; Writing by Tracy Rucinski; Editing by Julien Toyer and Keith Weir)