Online auctioneer eBay Inc. will begin auctioning advertising airtime on 2,300 participating U.S. radio stations. The company will partner with privately held Encino, Calif.-based Bid4Spots Inc., which has been hosting weekly online auctions of radio airtime since January 2005.

The auctions, for which eBay will receive a commission for each dollar spent on ad buys, will take place on eBay Media Marketplace, which also brokers cable-television ads.

This new partnership will place eBay in a head to head battle with Mountain View, Calif.-based Google, who in April announced it would sell ads on hundreds of stations owned by Clear Channel, in addition to Softwave Media Exchange, which has a slightly different model for selling radio's unsold advertising inventory and works with all the top groups in every major market and on over 1,700 radio stations in 288 markets.

"By combining this radio station base with eBay's reach and scale among potential advertisers, we believe we have the opportunity to create a vibrant new marketplace that will benefit the radio industry and advertisers alike," said eBay spokesperson Hani Durzy.

Wasting no time, eBay will begin taking bids for radio ads starting Wednesday.