CHICAGO -- The Tribune Co. has reached a written agreement to sell the Chicago Cubs, Wrigley Field and other assets to the family of TD Ameritrade founder Joe Ricketts for about $900 million, a person close to the negotiations said Monday.

The agreement was reached over the weekend and a document outlining the deal -- called a term sheet -- was sent to Major League Baseball for review, according to the person, who spoke on condition of anonymity because the agreement had not been announced.

The term sheet is not a final agreement, according to the person, who added that it contains details on how the Ricketts family will finance the deal. The deal also would give the Ricketts family a 25 percent interest in a regional cable television sports network.

Tribune Co. would not confirm an agreement had been reached.

"We continue an active dialogue with the Ricketts family with an eye toward reaching a definitive agreement," spokesman Gary Weitman said in an e-mail. "We don't intend to comment on the specifics of any potential transaction."

The team has been on the market since 2007, when real estate mogul Sam Zell announced his $8.2 billion purchase of Tribune Co. The financially troubled media giant filed for bankruptcy last December but the Cubs were not included in the filing.

Tribune Co. announced in January that the Ricketts family bid had been selected over two others for the team.

Cubs fans have greeted the news enthusiastically, in part because the Ricketts family in general, and the family point man in the bid in particular, are viewed as loyal Cubs fans.

Tom Ricketts has figured prominently in the selection process, from his days living across the street from Wrigley Field to the day he met his wife in the bleachers of the storied park. Ricketts fueled the perception that he is among the loyal with his initial public statement about the plan to purchase the team.

"We share the goal of Cubs fans everywhere to win a World Series and build the consistent championship tradition that the fans deserve," Ricketts said at the time.

But negotiations lasted longer than expected, complicated by factors such as Tribune Co.'s financial straits as well as the Ricketts' efforts to secure financing during the recession.

On Monday, though, Cubs manager Lou Piniella expressed optimism about the deal.

"I'm glad to see that things are progressing," he said. "Yeah it's a positive thing for this organization. It's been a while. It was good news. I heard it when I came to the ball park and I was very pleased."

Piniella said he has not met Tom Ricketts, but "I heard he's a fine gentleman and will be a really nice owner."