American Airlines (AA) is suing Google Inc over the Internet firm's sale of keyword ads for rivals trig-gered by its own trademarks.

A Google visitor who enters certain words or phrases that AA trademarked -- for example, Aadvantage, the name of its frequent-flier program -- will get links to AA's Web site but also its rivals under "sponsored links" -- targeted ads that appear alongside the regular search results.

Google makes most of its money from such keyword ads.

AA filed a lawsuit on Thursday in US District Court seeking unspecified damages.

"When done right, search is a great tool, but we have a problem with this part of their business," AA spokesman Billy Sanez said.

Sanez said the results could confuse consumers and divert customers away from AA's own site.

American Airlines, a unit of AMR Corp, tried to negotiate a settlement with Google before going to court, Sanez said.

Google spokesman Jon Murchinson said the company is "confident that our trademark policy strikes a proper balance between trademark owners' interests and consumer choice, and that our position has been validated by decisions in previous trademark cases."

Similar lawsuits against Google are fairly common, although they tend to involve smaller companies.

More than two years ago, a federal judge ruled in a similar case filed by insurer Geico Inc, ruling that Google's advertising practices were legal. Geico had said Google was letting rival insurance companies pay to have their ads displayed when a user searched for "Geico."

But the judge left the door open for Geico to collect damages from Google for featuring ads that used Geico's name in the text, rather than just using the trademark to trigger the ad. The two settled in 2005.

Google lost cases in France, but has won others in the US.