Kelleher bought the 2.2-acre site on North Water Street, adjacent to Lake Shore Drive for over $64m. Anglo Irish Bank is providing the financing for the site acquisition The luxury hotel and condominium skyscraper to be built on the site was first approved a year ago by the Chicago developer Christopher T Carley, Chairman of real estate firm Fordham Company but Carley struggled to finance the project.

The 124-storey tower will reach to about 610m (2,000ft ) to the top of its spire, surpassing Chicago's Sears Tower and the CN tower in Toronto.

Kelleher plans to start work early 2007 and complete building by 2010.

The $1.2bn ( 946m) development will include a five-star hotel and 300 luxury condominiums with unparalleled views through floor-to-ceiling windows, ranging from $600,000 ( 473,000) to $5m ( 3,945,000). Approximately 50,000sq ft of retail and support space is planned for the floors overlooking the river and Lake Michigan.

Calatrava's design is a tall, slender glass-fronted tower corkscrewing to the sky. Its twist is achieved by rotating each floor slightly more than 20 from the one below. Floors turn 2700 around the core as they rise, giving the facade and impression of movement.

Kelleher is one of Ireland's leading property entrepreneurs. He lived in Chicago for 10 years from 1986 and made his fortune renovating rundown buildings before leaving in 1996 to return to Ireland.

A spokeswoman for Shelbourne Development said this is the tallest and biggest single project that Kelleher has worked on adding, "he likes the building but it's too early to say whether he will make any changes to the plan".

One of the most difficult aspects of the project has been financing. It is believed that there will be further negotiation with all parties following the purchase. Kelleher's Chicago attorney Thomas J Murphy said that while he may have paid for the land he is not assuming unpaid bills for fees owed to the architect and other consultants.