Madrid regional premier Esperanza Aguirre had earlier this week promised to change "all the rules that need to be changed" to bring a US tycoon's vision of Las Vegas to Madrid. However, in the face of growing opposition to the complex, Aguirre cut a more circumspect figure on Wednesday.

"There are some demands that we can meet and others that we can't," Aguirre said. "People of my age don't like Las Vegas, but it has changed a lot. It now has sports, culture, ballet [...] We are not talking about a casino, but a great conference center."

The project would create enough jobs to halve regional unemployment, Aguirre said, while noting that Barcelona is also interested in hosting the complex.

Candidate sites for the Spanish Las Vegas include Valdecarros and Alcorcón. Finance Minister Cristóbal Montero denied that the new center would enjoy tax breaks.