(AP) -- If you're thinking of buying a 3-D television set this year based on the belief that you'll be able to purchase a lot of the 3-D movies that have hit theaters in the past few years, think again.

U.K. research firm Screen Digest says 70 percent of the 25 3-D movies expected to be available this holiday season will be tied to the purchase of a TV from a certain manufacturer.

For example, a Sony 3-D TV buyer won't immediately be able to watch DreamWorks Animation's "How To Train Your Dragon" because that movie will be tied to the purchase of a set from Co.

Screen Digest says that so far, only three Hollywood movies, including The Co.'s "A Christmas Carol," and three documentaries will be available on retail shelves without being tied to a specific TV brand.

The firm presented its findings at the 3D Entertainment Summit in Los Angeles on Wednesday.

Although buyers of 3-D TVs can appreciate that bundled movies will allow them to try out their new TV immediately, a lack of broadly available titles could hinder the adoption of 3-D watching in the home, said Helen Davis Jayalath, an analyst with Screen Digest.

"The exclusive bundling deals can't go on for too long, or it's going to be a problem," Davis Jayalath said after her presentation. "Hopefully these licensing deals will expire soon."

Jeffrey Katzenberg, the chief executive of DreamWorks Animation SKG Inc., said it will take "another year or two" before enough homes have 3-D TV sets for it to make sense to release 3-D Blu-ray movies without such bundles.

"For us, we felt that the greatest opportunity is to partner with Samsung," he said in an interview.

Although 3-D movies have already given a lift to revenue from theaters, it could take a while for 3-D TVs to really take hold. Screen Digest said by 2014, about 28 percent of TV-owning households in the United States will have a 3-D TV.

Katzenberg said he expected 3 million 3-D TVs would be sold in North America this year.