The U.S. Supreme Court turned away an appeal by Bank of America Corp., Citigroup Inc. and JPMorgan Chase & Co., refusing to stop antitrust lawsuits that accuse some of the world's largest banks of conspiring to rig Libor.

The banks sought review of a decision that said the suing investors had adequately claimed they were harmed by the alleged effort to drive Libor down. The investors held securities tied to Libor, or the London Interbank Offered Rate, an interest-rate benchmark used to value more than $300 trillion of securities worldwide.

The federal appeals court left open the possibility that the antitrust claims in Manhattan could be dismissed on other grounds. Even so, the Supreme Court rebuff leaves the banks vulnerable to the prospect of billions of dollars in damages should the suits succeed.