The project has excited cash-strapped politicians who are facing massive unemployment and shrinking revenue from an economy sliding in to its second recession in three years.
"Spain has the same tributary laws as anyone ... subject to European norms. But in the future these norms, of course, could be revised, modified, to attract investment," Montoro told Parliament when asked how he saw the U.S. groups' request for preferential tax laws.
Las Vegas Sands said in February it was studying an investment of as much as 15 billion euros (us$ 20 billion) over 10 years in the complex, which would include 36,000 hotel beds, 18,000 slot machines and three golf courses.
Local press has reported the company wants free use of public and private lands, government investment in infrastructure to support the casino complex and 10 years of tax breaks.
One report in El Pais said the group wanted changes to Spain's labour laws, lower social security payments, relaxed smoking laws and the creation of university degrees in casino management.
"EuroVegas" Managing Director Michael Leven said on Tuesday in an interview in El Mundo the group was 90 percent sure it would bring the project to Spain.