In the expanded world in which Comcast Corp. now finds itself, Harry Potter is a precious property - and the company is likely to have to pay top dollar for the world-famous wizard.

Comcast must consider purchasing the 50 percent ownership in the Universal theme parks in Orlando that it does not already own. The seller is the private-equity firm Blackstone Group.

The Philadelphia cable company has until June 12 to decide, according to terms of a contract with Blackstone.

The possible deal was first reported Tuesday morning by the website TheWrap.com. Wall Street analysts have also been talking about a sale.

Comcast could pay between $1 billion and $1.5 billion because of the popularity of the new Wizarding World of Harry Potter attraction at the Universal-owned Islands of Adventure park. The other theme park in the deal is Universal Studios Florida. Comcast obtained its 50 percent ownership of the theme parks when it purchased control of NBC Universal Inc. in January.

Paid attendance at the two parks rose 20 percent, to 11.2 million, in 2010, a surge attributed to the Harry Potter attraction, which opened in June 2010.

Blackstone informed the Philadelphia cable company of its decision to sell the half-ownership in Universal City Development Partners Ltd. earlier this year, and Comcast may find itself unable to say no.

Under contract terms that Comcast inherited when it acquired control of NBC Universal, the cable company must purchase the Blackstone stake or risk losing the business. That's because Blackstone would be allowed to sell the entire theme-park enterprise, including Comcast's piece of it, to a third party if Comcast declines to close a deal with Blackstone.

Comcast had no comment. Blackstone could not be reached for comment.

"It's a fine operation and it helps, I think, to support the Universal brand," said David Joyce, an analyst with Miller Tabak + Co. L.L.C.

"It would put some more debt on the balance sheet, but it's not a big deal."

Keeping the Universal theme parks would preserve a business model also used by the Walt Disney Co., which owns and operates movie studios and theme parks. Disney and Universal earn extra revenue from the intellectual property associated with popular movies through theme-park attractions and related merchandising sales.

The last Potter movie, Harry Potter and the Deathly Hallows Part 2, is scheduled to be released July 15, which may be a factor in Blackstone's decision to cash in now.

A deal with Blackstone would come shortly after Comcast borrowed to complete its merger with NBC Universal and as it seeks to improve the ratings for NBC's dismal fourth-rated prime-time slate. Comcast has said it will spend $200 million this year alone to improve NBC's prime-time shows, mostly for the 10 p.m. time slot.

The Universal theme-park business had a strong year in 2010, with $1.1 billion in revenue and $148 million in net income. Prior-year revenue was $802 million and net income was $23.5 million. The issue, analysts say, is whether the theme parks can sustain the attendance gains and profits as the novelty of the Harry Potter attraction wears off.

"There is a lot of buzz around Harry Potter," Neil Begley, senior vice president and analyst with Moody's Corp., said earlier in the year. "Blackstone may be thinking this is a peak and there is downside risk."

Most observers thought Comcast would have several years to decide whether to stay in the theme-park business, but it has had only several months.

Contact staff writer Bob Fernandez at 215-854-5897 or bob.fernandez@phillynews.com.