WASHINGTON (Legal Newsline)-The U.S. Supreme Court on Tuesday said it would not rule on whether ExxonMobil must pay interest on an award to victims of the 1989 Exxon Valdez oil spill.

The nation's high court said the question should be decided by the 9th U.S. Circuit Court of Appeals in San Francisco.

If Irving, Texas-based oil company is made to pay interest on the award it would nearly double the $507 judgment the Supreme Court approved in June.

Exxon has argued it should not have to pay interest on the award, saying there is "no good reason" for the high court to add interest to the judgment.

"Exxon does not agree that there is any sound basis to award plaintiffs what they seek -- approximately $488 million over and above the $507.5 million that this Court determined was the legally proper amount to punish and deter," Exxon's filing to the high court said.

Judges have discretion in whether to award interest payments. In the federal courts, rules say that interest payments are calculated by a certain Federal Reserve rate available at the time of the award. In the Exxon case, that rate was 5.9 percent.

An attorney for the plaintiffs has said his clients are owed about $488 million in accrued interest since an Anchorage jury awarded them $5 billion in 1994 for the historic oil spill.

That award, however, has been slashed by the federal courts.

In 2006, the 9th U.S. Circuit Court of Appeals reduced the award to $2.5 billion. Exxon then appealed to the U.S. Supreme Court.

A divided Supreme Court in June reduced the $2.5 billion punitive damages award in the long-running lawsuit to no more than $507.5 million, ruling 5-3 that the original award was excessive.

"The award here should be limited to an amount equal to compensatory damages," Associate Justice David Souter wrote for the majority.

From Legal Newsline: Reach reporter Chris Rizo at chrisrizo@legalnewsline.com.