Google announced its intention to break into radio ads with an agreement to buy DMarc Broadcasting for as much as $1.24 billion.

Google will pay $102 million in cash for closely held DMarc and make additional payments of as much as $1.14 billion if sales meet targets over the next three years, Mountain View, Calif.-based Google said yesterday in a statement.

The purchase is part of Google’s strategy to replicate its success in selling Internet advertisements to other media including print and radio. The company plans to integrate DMarc’s software with its own online auctions for selling Internet ads, giving it access to the $11 billion radio advertising market.

“This acquisition provides further evidence that Google is serious about extending its AdWords platform beyond Internet media,” a JPMorgan analyst, Imran Khan, said yesterday in a note.

“Google’s efforts to extend its advertising model into traditional media could pay off over the longer term.”

Google, the most-used Internet search engine, said it expects to complete the transaction by the end of the first quarter.DMarc is based in Newport Beach, Calif. DMarc’s technology allows companies to submit their ads over the Internet and buy spots on radio stations across the country. The software also lets advertisers direct individual ads to specific markets and can track how many people respond to the spots, according to the company’s Web site.

Ads sold by Google started appearing in print magazines including PC Magazine and Maximum PC in August. Google said at the time that it was conducting a “limited test” of the new sales strategy.

American companies spent a total of $11 billion on radio ads in 2004, according to TNS Media Intelligence, which tracks advertising spending.

Google in September raised $4.18 billion in a stock sale, sparking speculation it may make acquisitions to add new products. The company has since agreed to spend $1 billion for a 5% stake in Time Warner’s AOL unit.