CHICAGO – Tribune Co. and its CEO Sam Zell rejected an Illinois state agency’s plan to buy Wrigley Field and are pushing ahead to sell the ballpark together with the Chicago Cubs, a top company official said Tuesday.

Crane Kenney, the Cubs’ chairman and outgoing general counsel of parent Tribune, said there still is a chance Wrigley could be sold separately to the Illinois Sports Facilities Authority.

But after months of talks with the ISFA that have failed to produce an agreement, he confirmed Tribune is moving ahead to package the stadium together with the ballclub in a private sale that outside experts believe could fetch as much as $1 billion for the cash-crunched media conglomerate.

“We’ll continue to work with city and state officials if there is a transaction that makes sense for the Cubs, Tribune and the public,” Kenney said in an e-mail. “We are also moving the private process forward and expect to have the descriptive memorandum in the market within the next two weeks.”

That memorandum, also known as the financial books, will give the half-dozen or so groups of prospective buyers their first detailed information about the Cubs and Wrigley.

The would-be bidders had expected to have those figures by now. Zell said on an April 17 conference call with investors that the books were expected to go out to Major League Baseball-approved bidders within 2« weeks from then, which means the already-dragging process has run into further delays.

Zell first stated his intentions to sell the Cubs and Wrigley more than a year ago as part of his agreement to take control of Tribune.

His decision to nix the ISFA’s recent $400 million proposal was first reported Tuesday by the Chicago Sun-Times. The newspaper, citing unidentified sources, said Tribune executives had concluded that its novel plan to raise financing without increasing taxes – by selling equity seat rights at Wrigley – could violate both Internal Revenue Service code and MLB rules.

Kenney did not elaborate on the decision. Both a Tribune spokesman and a Zell spokeswoman declined comment and ISFA’s executive director, former Gov. Jim Thompson, did not immediately return a call.

The Sun-Times reported the IFSA plan called for selling several thousand seats to raise money for ballpark renovations. The ballpark purchase could have been covered by state bonds backed by future ticket revenue.