* Colombia's ISA to buy 60 percent of Cintra Chile

* Deal includes call option on remaining 40 percent

* 250 million euro potential net capital gain for Cintra

* Ferrovial shares up 1.6 percent

(Adds details on capital gains, share price)

MADRID, Dec 29 - Spanish toll road firm Cintra has agreed to sell 60 percent of its stake in Cintra Chile to the Colombian ISA Group for 209 million euros ($300.7 million), its parent Ferrovial (FER1.MC) said, in a move to cut debt.

It said ISA will have a call option on the remaining 40 percent of the company, implying a potential net capital gain for Cintra of some 250 million euros that would be booked in 2010.

The agreement fits into our strategy of raising additional funds by selling more mature assets in our portfolio in order to use the proceeds for new projects with strong value-creation potential, Cintra's Chief Executive Enrique Diaz-Rato said in the statement on Tuesday.

This year, Ferrovial has sold London's Gatwick airport for 1.66 billion euros and Cintra's car park division for 451 million euros.

By 0926 GMT, Ferrovial's shares gained 1.6 percent to 8.06 euros, the best performer on Spain's blue chip index .IBEX. ($1=.6951 Euro) (Reporting by Tracy Rucinski; Editing by Jon Loades-Carter and Hans Peters)