NEW YORK (CNNMoney.com) -- Some of the nation's largest wireless companies are starting to allow advertising on their cell phone networks, according to a report published Wednesday.

The Wall Street Journal reports that Sprint Nextel (Charts) and Verizon Wireless are running trials of banner ads on their wireless information and entertainment services.

"We are testing out some different models," Jeffrey Nelson, a Verizon Wireless spokesman, told the newspaper. "We're going to continue to assess them."

In addition, Yahoo! (Charts) is set to announce a deal Wednesday to put its listings on the go2 Directory local-search Web site carried by those two providers as well as No. 1 cell phone service Cingular Wireless, according to the report.

The Journal reports that to this point most wireless Internet sites don't include advertising. But with operators now starting to include ads on their own sites, the amount of wireless Internet advertising is expected to mushroom, according to the newspaper.

Cell phone companies are eyeing ads as a way to combat declining revenue from voice calls, where the are cutting prices to attract customers, the paper reports.

It also says that media companies that are investing heavily to bring sports, news, videos and other entertainment to wireless devices are also pressuring the cell phone providers to run ads to supplement what has been disappointing sales of the services so far from cell phone customers.

Cingular is a joint venture of AT&T (Charts) and Bell South (Charts), while Verizon Wireless is a joint venture of Verizon Communications (Charts) and Vodafone Group (Charts)

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