US top court won't hear Pimco market squeeze case

* At issue U.S. Treasury note futures

* Lawsuit seeks more than $600 million in damages

WASHINGTON Feb 22 (Reuters) - The U.S. Supreme Court on Monday denied an appeal by Pacific Investment Management Co challenging class-action certification for a lawsuit alleging the world's largest bond fund manager tried to corner a market for U.S. Treasury note futures.

A U.S. appeals court in Chicago upheld a judge's ruling that certified as a class more than 1,000 investors who seek more than $600 million in damages.

Pimco, a Newport Beach, California-based unit of the German insurer Allianz SE (ALVG.DE), appealed to the Supreme Court, but the justices turned down the appeal in a brief order without any comment.

The lawsuit accused Pimco of boosting its percentage stake in futures contracts on some 10-year Treasury notes to 42 percent from 12 percent over a two-week span in the spring of 2005. The relevant contracts traded on the Chicago Board of Trade.

In its appeal to the Supreme Court, Pimco argued that class-action status should not have been granted because some plaintiffs did not lose money and the class suffered from serious conflicts of interest that precluded certification.

Attorneys for the investors urged the Supreme Court to reject the appeal and said the fact-bound determination in the case does not conflict with any decision by the high court or any other appeals court. They said the case should be allowed to go forward. (Reporting by James Vicini, Editing by Dave Zimmerman)