Troubled Spanish builder Sacyr Vallehermoso announced on Monday the sale of its highway operator Itinere to Citigroup in a 7.88-billion-euro deal that will give it some relief from its huge debts. But the construction group said it would continue to seek a buyer for its 20.01-percent stake in Spanish-Argentine oil major Repsol YPF, in which Russian oil giant Lukoil has controversially shown interest. Sacyr said Citi Infrastructure Partners will buy 100 percent of Itinere for 3.96 euros per share, or 2.87 billion euros (3.63 billion dollars) and assume 5.01 billion euros of its debts, Sacyr said. Sacyr's debt, which stood at about 19 billion euros at the beginning of the year, is threatening the survival of the group, one of Spain's biggest construction firms. Spain's once-booming construction industry was the engine of its economic growth in the past decade. But the property market began to collapse last year amid rising interest rates and the international lending crunch. The sale of Itinere will reduce Sacyr's debt to around 12 billion euros, and "the net corporative short and medium term debt will fall to zero," said Sacyr's managing director Ana de Pro, in an indication that the company will be able to service its debt. Its massive debts have already pushed Sacyr to put its stake in Repsol YPF up for sale. But Lukoil's interest has sparked concern in Spain, with the conservative opposition party accusing the government of nothing to prevent a "dubious" company with ties to the Kremlin from controling the country's leading oil group. Asked at a news conference whether Sacyr would continue to seek a buyer for its Repsol stake, De Pro replied "obviously." The ABC newspaper Monday said other potential buyers include the Kuwait Investment Authority and the China National Petroleum Corp (CNPC). Citigroup also reached a separate agreement to resell certain Itinere concessions in Spain, Portugal, Brazil and Chile to infrastructure groups Abertis of Spain and Italy's Atlantia. Abertis said it would pay Citigroup 621 million euros, while Atlantia said it would hand over 420 million euros. On the Madrid stock market, Sacyr shares were up 3.57 percent at 7.83 euros by 1151 GMT, while Repsol was down 2.57 percent at 14.81 euros, in a market that had dropped 2.70 percent.