Google said today that it planned to acquire Internet advertising company DoubleClick for $3.1 billion, in a deal that will expand the search firm's presence into online banner advertising and raise the stakes for competitors such as Yahoo and Microsoft. The purchase, which Google said will be made in cash, will accelerate the Mountain View, Calif., company's effort to extend its business beyond the small text ads that appear next to Web search results. Microsoft had been trying to outbid Google for DoubleClick, an online ad broker that sells banner and video Web ads. Yahoo also competes in the market. Another large DoubleClick competitor, Advertising. com, is owned by AOL, a division of Time Warner.

Internet advertising spending rose 17 percent last year from 2005, to $9.8 billion, far faster than traditional media, according to TNS Media Intelligence, an advertising research firm.