NEW YORK (AP) _ The predictions have been worse than the reality so far, but U.S. TV makers are worried about a shortage of glass for picture tubes.

With the biggest selling season for TVs - the holidays and sports-heavy January - still ahead, executives wonder if the problem will affect the availability of some models.

''Worldwide supply of glass is not now sufficient to support the demand we're seeing,'' said Gerald McCarthy, executive vice president of sales and marketing for Zenith Electronics Corp.

The problem came partly because several furnaces used to make TV glass went through maintenance simultaneously this spring, reducing the industry's total capacity.

In addition, higher demand of bigger-screen TVs is a strain because the amount of glass rises geometrically as screen sizes grow. A 19-inch TV has a glass panel weighing 16 pounds while a 35-inch TV has one of 75 pounds.

''Your unit capacity actually goes down even though your tonnage is remaining constant,'' said Tim Hickey, chief executive officer of Techneglas Inc., a Columbus, Ohio, company that is the nation's largest maker of TV glass.

And as TV makers try to give more choices to consumers, they have started asking glass manufacturers for a second, darker tint that improves resolution. Some TV model lines also have up to five different contours of screen glass.

''That's five sets of molds we have to invest in,'' said Duane Welch, director of planning and development in the information display group at Corning Inc. ''And we lose production time when we have to change them.''

New plants in the United States and overseas are not expected to ease the glass crunch until late next year.

Ends adv for Monday, Aug. 29