PASADENA, Calif. – NBC’s “Today” show will add a fourth hour in September, stretching television’s most popular and lucrative morning show nearly into lunchtime.

The fourth hour will likely resemble the current third hour, light on hard news and heavy on lifestyle segments, NBC executives said yesterday. Al Roker and Ann Curry are currently hosts of the third hour, but NBC News President Steve Capus said it hasn’t been determined who will do the fourth hour.

“The key here is the quality,” said executive producer Jim Bell. “It will connect with the `Today’ brand.”

At the same time, NBC is canceling the soap opera “Passions.” Both moves reflect a trend that advertisers have less interest in traditional daytime TV while morning news and entertainment is considered a growth area. Fox is introducing a new network morning show on Monday.

Roughly half of NBC affiliates are expected to take the fourth hour when it begins, Capus said. Some may air it at a different time of day.

“Today” host Matt Lauer, who will likely have little to do with the fourth hour, acknowledged that he was wary about the idea at first.

“You go into something like this with slightly mixed emotions,” he said. “The one thing you don’t want it to do is dilute the brand.”

But he said he understood the business reasons behind it and was confident it will work.

Lauer’s co-host Meredith Vieira will have nothing to do with the fourth hour for contractual reasons. Since she is host of the game show “Who Wants to Be a Millionaire,” her contract forbids her from being a part of another show past 9 a.m. each day.

Capus also said he expected better results from the fourth hour than the short-run “Later Today” program, which aired earlier this decade with Florence Henderson as a host.

That show didn’t work because it felt like something different from the “Today” show, he said.