Zell said during a conference call with lenders that separate bids have been made on storied Wrigley Field, the nation's second-oldest baseball stadium. The team's sale must be approved by Major League Baseball.
"We hope to have a deal to MLB by the end of the year," said Zell, the real estate mogul who led an $8.2 billion buyout of the company last year. He said he expects "rapid" approval.
Tribune is selling the ballpark, baseball team and a 25 percent interest in a local sports channel to raise cash to pay down $13.4 billion in debt, mostly related to the buyout.
Major League Baseball in June sent out financial books on the three properties to nine pre-approved bidders.
The list reportedly included a group headed by John Canning, chairman of private equity firm Madison Dearborn Partners LLC; Internet billionaire and Dallas Mavericks owner Mark Cuban; and the family of online brokerage Ameritrade's founder, Joe Ricketts.
People familiar with the process -- who declined to be named because of confidentiality agreements -- told The Associated Press after the deadline for initial bids passed July 18 that Tribune had narrowed the field to five.
In the conference call Tuesday, Zell assured lenders the company is on track to meet a $593 million debt payment in June.
Tribune already repaid $807 million in principal in the second quarter, using mostly the $600 million it gained from selling the Long Island daily Newsday to Cablevision Systems Corp.
Zell also said the company is continuing to evaluate ways to squeeze money from its real estate holdings, including the iconic headquarters building in Chicago, Tribune Tower.
To trim costs, Tribune has made hundreds of layoffs at its papers and decreased the page count of print editions.
Zell said the company is still trying to figure out "what a newspaper of the 21st century should look like." While redesigns should produce "more exciting and cheaper" versions of its papers, he said the company would have to readdress the matter if the revamped papers don't get a positive response.
Fitch Ratings cut Tribune Co.'s credit rating further into "junk" status Friday -- to "CCC" from "B-" -- and said more reductions may come within a year if newspaper advertising revenue declines keep accelerating.