Envisioning a lucrative wireless search and advertising market, U.S. cellphone companies are shying away from deals with Internet giants such as Google Inc. and Yahoo Inc. in favor of partnerships with small start-ups they can more easily control.

Google, Yahoo and other Internet companies are targeting wireless search as a major new growth area as cellphone use proliferates globally. They see billions of dollars in potential revenue from selling advertising that is linked to searches for ringtones, games, local listings and mobile Web content.

The search giants have had some success overseas, but they have still had difficulty penetrating the large U.S. carriers, which ultimately control access to the nation's nearly 217 million cellular subscribers.

Large phone companies, including Verizon Communications Inc. and AT&T Inc., never really profited from the explosion of search and advertising on the Internet. Now wireless operators like Verizon Wireless and Cingular Wireless, which are partly owned by those same phone giants, don't want to make the same mistake.

Verizon Wireless, a joint venture of Verizon and Vodafone Group PLC, is putting the finishing touches on a deal with Seattle-based mobile-search provider Medio Systems Inc., people familiar with the situation say. Verizon's users will be able to search for downloadable multimedia content through a Medio-powered search bar. Medio is also developing a service to allow ads based on search results, similar to the model Google and Yahoo have pioneered on the Internet.

Another small search provider, JumpTap Inc. of Cambridge, Mass., says it has struck early-stage search deals with several North American carriers that together account for 75 million subscribers. JumpTap would not disclose which carriers it is working with, but people familiar with the situation said one was Cingular Wireless, a joint venture of AT&T and BellSouth Corp. and the largest U.S. carrier by subscribers. Cingular declined to comment on its strategy surrounding search services.

Alltel Corp., the fifth-largest U.S. cellular carrier, has narrowed its selection of a search partner to JumpTap and Medio, a top company executive said.

It's still early, and the carriers haven't committed to developing a full suite of potential search services with any partner. In fact, Google and Yahoo could still score some major wins. Yahoo, for example, has a partnership with AT&T and might move closer to Cingular if AT&T completes its acquisition of BellSouth and takes full control of the cellular company.

The early deals are taking place as cellphone operators recognize that wireless Internet search is an inherently different business than its wired counterpart. Whereas people might use a Web-connected personal computer to search for information about an 18th-century British author, they are more likely to use cellphones to find targeted information like news, weather and sports. Cellphones also offer much less space to enter in search terms and smaller screens to display results.

Some of the advancements by the major portals in Internet search, such as Google's famous page-ranking scheme, don't apply in the wireless world since people aren't searching for Web sites as much as answers to specific questions. Alltel's group president of operations, Kevin Beebe, says the Internet search giants aren't yet delivering the kind of results he wants. "What they're trying to do is take that core search capability and just jam it onto the phone," Mr. Beebe said. "That's probably not the right approach."

But the Internet companies say they are putting significant resources and effort into tailoring their technology for cellphones. "We have thought specifically about mobile search," says Deep Nishar, director of product management at Google. "We know it's about finding, not browsing."

Consumers can already perform basic searches on cellphones using the mobile Web sites of Yahoo, Google, and others. They can also use text-message-based services. But the wireless operators are developing more powerful services that will be integrated on customers' handsets and allow searching of everything from the mobile Web to local listings to downloadable multimedia content such as ringtones and games.

These more advanced services, which are likely to be rolled out in phases beginning sometime later this year, promise to open up a range of new revenue opportunities for cellular operators. Wireless carriers know a great deal of information about their subscribers, which is valuable to advertisers. In addition, advertisers may be willing to pay more if consumers actually "click to call" a company whose ad they are interested in.

Eric McCabe, JumpTap's vice president of marketing, says he expects advertisers to pay about 35 cents to 50 cents when a cellular subscriber clicks on a sponsored link, but as high as $7 when the consumer calls the advertised company.

Advertising is a $12.5 billion market on the Internet, according to market-research firm eMarketer, and many industry analysts predict it has the potential to be extremely lucrative on cellphones as well. The potential revenue from third parties such as advertisers will be increasingly important for wireless operators as revenue from voice services declines. The carriers hope that growing consumer subscriptions to premium data services, such as multimedia downloads, will help as well.

By aligning themselves with start-up search companies, the carriers believe they will keep a greater share of the generated advertising revenue, say people familiar with the matter. The wireless companies also worry that their brands will be diluted if they gave a prominent marketing slot to a major Internet brand.

"The Internet players are going to demand a much different set of economics than we will," says Medio Chief Executive Brian Lent, who worked with Google founder Sergey Brin in the 1990s at the Stanford lab that spawned the search engine.

Google and Yahoo have had more success with carriers in Europe and Asia. Google, for example, has deals with Britain's Vodafone and KDDI Corp. in Japan. Yahoo has a search deal with British carrier Hutchison 3G UK Ltd. Both Internet giants also have agreements with large handset manufacturers such as Motorola Inc. and Nokia Corp. to include their search technology in phones. But the deals don't necessarily help them, because U.S. carriers ultimately decide what phones consumers can purchase. "We design our own phones, so we aren't shackled to what Motorola presents us," says John Styers, director of data programming and planning for Sprint Nextel Corp., the third-largest U.S. carrier.

Google and Yahoo say carriers will eventually discover the start-ups can't handle large amounts of user requests. The portals' biggest advantage, besides years of experience developing search technology, is that they already have a sales force and network of advertisers in place. "It's going to be very difficult for a small player to build a brand-new advertising network," says Steve Boom, senior vice president of Yahoo's broadband and mobile business.

Sprint's Mr. Styers says he believes carriers face a trade-off: Though they might get a better revenue share in the future with smaller partners, they would likely have to spend more to create an ad network and perfect the search infrastructure. He says Sprint hasn't decided which route it will ultimately choose.