NEW YORK — Two small, long-struggling television networks — UPN and The WB — will shut down this fall and programming from both will be used to launch a new network aimed mainly at young and minority viewers.

The new network will be called The CW — "C" for CBS Corp. and "W" for Warner Bros. — each of which will own half of the new entity and contribute programs, assets and executives to the venture.

The new network will draw on programming from UPN, whose shows include "Everybody Hates Chris" and "Veronica Mars," as well as from the slate of The WB, which includes "Supernatural," "Smallville" and "Everwood."

Tribune Co., a Chicago-based media company, will relinquish its 22.5 percent stake in The WB in exchange for a 10-year affiliation deal to carry the new network on 16 of its stations. The rest of The WB was owned by Time Warner Inc., parent of Warner Bros.

The CW also will be carried on 11 stations owned by UPN, a unit of CBS Corp., guaranteeing the network carriage in about 47 percent of the country and 20 of the top 25 TV markets. Network executives said they hoped to have agreements in place to cover most of the rest of the country by the time it launches in the fall.

UPN and The WB struggled to compete against larger rivals in the broadcast TV business, including Walt Disney Co.'s ABC, General Electric Co.'s NBC, CBS Corp.'s CBS and News Corp.'s Fox. Both place consistently behind their larger rivals in the Nielsen ratings race and have been financial burdens on their parent companies.

Barry Meyer, the head of Warner Bros., said at a news conference his company had anticipated a "challenged" environment ahead for smaller networks, and said the new venture had a good chance of being profitable as soon as it launches. He said the companies would operate more efficiently as one, but he declined to say how much savings they expected to get or how many jobs might be cut.

"Looking down the road, this was much better than keeping UPN alive," said Leslie Moonves, the chief executive of CBS. CBS became a separate company from Viacom Inc., the owner of MTV and VH1, at the beginning of the year.

However, it's not yet clear that the combination of two struggling networks will result in a strong one, or even one that is a money-winner. Hal Vogel, a longtime media analyst and author of a book on entertainment industry economics, called the combination "inevitable," saying "these companies were not making money for anybody."

"Chances are, in five years they may not exist at all, or it may be something else, but right now it's better than going alone," Vogel said. "This makes sense — it's not a slam-dunk proposition, but it makes sense. Six networks was too many."

The combination will trigger a shake-up of network affiliations in a number of cities. In the seven cities that have a Tribune-owned station and also one UPN-owned station, the companies already have divvied up which ones will carry the new network — Tribune stations in four markets, and CBS-owned ones in the other three.

In other cities that have WB affiliates and UPN affiliates that are not owned by either CBS or Tribune, it's not yet clear what will happen or what financial arrangements will be made. Meyer said the network would be looking at each market individually.

The deal also opens the question of what will happen to the nine UPN-affiliated stations that are owned by the Fox network's parent company, News Corp. Fox already has its own stations in most of those markets, and several of those cities also have stations that will become affiliates of The CW.

"We view this change as an opportunity for us," News Corp. spokesman Andrew Butcher said. "We'll be working hard over the next few months to reprogram prime time, and we'll be ready with a new slate in September."

The CW will air 30 hours of programming, seven days a week, following the model of The WB. Six nights of prime time shows will air Monday through Friday 8 to 10 p.m. and Sundays 7 to 10 p.m. There also will be shows on weekday and Sunday afternoons, and five hours of children's programs on Saturday morning.

The new network will be based in a new, yet-to-be determined location, network executives said. Both networks are based in Southern California, The WB in Burbank and UPN in Brentwood. Both networks launched in early 1995.

Dawn Ostroff, who is currently president of UPN, will become the president of entertainment at The CW, overseeing programming, while John Maatta will oversee business operations as chief operating officer. Maatta had been COO of The WB.