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.

On Friday, the U.S. central bank approved a half-percentage point cut in its discount rate on loans to banks to "promote the restoration of orderly conditions in financial markets."

The decision means the discount rate, the interest rate that the Fed charges to make direct loans to banks, will be lowered to 5.75 percent from 6.25 percent.

But the Fed did not change its target for the more important federal funds rate, the interest commercial banks charge each other on overnight loans. The benchmark interest rate has remained at 5.25 percent for more than a year.

In the statement announcing the interest rate cut, the Fed said it "is monitoring the situation and is prepared to act as needed to mitigate the adverse effects on the economy arising from the disruptions in financial markets."     

In 2003, Catalona became director of the Clinical Prostate Cancer Program at Northwestern University in Chicago, asking participants in former research efforts that he oversaw at Washington University if they would consent to transferring their tissue to Northwestern.

Donors of 4,000 tissue samples agreed to the transfer, but Washington University sued to keep the samples there, and won rulings from a U.S. District Court judge and the 8th U.S. Circuit Court of Appeals.

In papers filed with the U.S. Supreme Court, Catalona says he and the research participants could suffer irreparable harm if the appeals court decision is allowed to go into effect.

Washington University could use the tissue in studies the patients would find objectionable, or publish research results in a way that could identify the patients, Catalona's lawyers argued, raising the possibility that participants or their family members might be denied health, life or disability insurance.

In June, Dr. Larry Shapiro, dean of Washington University's School of Medicine, called the appeals court decision a precedent that assures the right of research institutions to use repositories without fear they will be taken or disrupted.

A dozen major research universities, as well as the American Cancer Society and associations of medical colleges and universities, had filed briefs supporting Washington University.

Catalona's lawyers asked Justice Samuel Alito to delay the appeals court decision until the full Supreme Court decides whether it will review the case.