LOS ANGELES (Reuters) - The struggling NBC network on Sunday announced 16 new TV shows - seven of them comedies - for the 2012-2013 season, and in a show of confidence said it will broadcast singing contest "The Voice" in the fall as well as the spring.

NBC, which has been the least-watched of the four major U.S. TV networks for several years, said it hoped the slew of new comedies would capture the young viewers most coveted by advertisers because of their spending power.

"We want to get more comedy on the schedule. I think it would be good for the health of the network," NBC entertainment chairman Bob Greenblatt told reporters in a conference call.

"We are adding several new comedies which we hope will portend the future of where we go with shows that are broader and more accessible and will garner a bigger audience," Greenblatt added.

NBC, majority-owned by Comcast Corp , unveiled the schedule a day ahead of an "upfront" presentation of its 2012-2013 schedule to advertisers. Some 75 percent of advertising sales are made in the few weeks following the upfront presentations.

Walt Disney Co's ABC DIS.N, CBS Corp's CBS CBS.N and News Corp's Fox NWSA.O present new shows later this week.

The new NBC comedies, which will start rolling out in September, include a family comedy set in the White House called "1600 Penn", a show about gay dads and surrogate parenting from "Glee" creator Ryan Murphy, and "Animal Practice" - a show about an unorthodox veterinarian in New York.

SHORTER ORDERS CUT COSTS

With so many new shows, NBC cut costs by ordering just 13 episodes of some of them, instead of the standard 22.

"Nothing would make us happier than to see this 13 episode order expand to 22 because they are doing well and then we really have an embarrassment of riches," Greenblatt said. "The only way to make the math work was to make some of these shows slightly smaller orders."

Old favorites, but those with declining audiences such as "The Office" and "30 Rock," will return, and Greenblatt said no decision had been made about how many more seasons those shows will enjoy on air.

NBC also ordered five new dramas including "Hannibal," based on fictional killer Hannibal Lecter, and four new reality shows.

During the 2011-12 season that is about to wrap up, the network season suffered a number of high-profile and costly failures including dramas "The Playboy Club", "Prime Suspect," "Awake" and comedies "Free Agents" and "Bent," all of which were canceled or are not returning.

Musical drama "Smash" and "The Voice" were the few bright spots. "The Voice" marks NBC's only entry in the Top 10 prime-time shows among the 18-49 age group most sought by advertisers.

NBC said "The Voice" would now air twice a season, starting with a slot in the fall on Mondays and Tuesdays ahead of returning Fox contest "The X Factor" on Wednesdays and Thursdays

Greenblatt said there was room for two competition shows at the same time and shrugged off buzz around the expected hiring of Britney Spears as a new "X Factor" judge in the fall.

"We just try to close our ears to what is going on out there and just focus on our own show. Everyone said we couldn't possibly launch 'The Voice' in the wake of 'American Idol,'", he said, referring to the two shows running concurrently this year.

"There was never any doubt that we were going to do two cycles a year (of 'The Voice') eventually after we got our sea legs," he said.

But Greenblatt said tweaks were underway at "The Voice" to keep audiences engaged. "We know people love the revolving chairs, and so we have a plan to get them into the battle rounds. There are also changes and tweaks in the format that will make it even better and more competitive."

"Smash," starring Debra Messing and Katharine McPhee and capturing the backstage drama of putting on a Broadway musical, has earned a loyal following and Greenblatt said he "Couldn't be happier" with Smash.

Among other the shows that will not be returning to NBC next season are legal drama "Harry's Law" - because NBC said its audience skewed too old - "The Firm," "Are You There Chelsea?" and "Best Friends Forever."

(This has been refiled to fix the Reuters Instrument Code in sixth paragraph)