A federal judge Thursday decided to rule within a month on a lawsuit brought by a former top auditor for the Interior Department that Kerr-McGee Corp. had cheated the government out of millions of dollars in royalties.

A jury agreed with auditor Bobby L. Maxwell last month, saying the Oklahoma-based oil company had undervalued the oil it produced in publicly owned coastal waters and consequently paid lower royalties. The jury said Kerr- McGee underpaid about $7.6 million.

Judge Phillip Figa said he'd make a ruling within 30 days, although he urged the parties to inform him within seven days if they can discuss a settlement.

"Whatever I decide won't end the case," Figa said, speculating it could go to higher courts.

Maxwell alleges Kerr-McGee, now a part of Anadarko, cheated the federal government out of millions of dollars in royalties between 1997 and 2002 by knowingly selling oil produced in the Gulf of Mexico at below-market prices to a company that, in exchange, absorbed much of its marketing costs. Kerr-McGee denies any wrongdoing.

"A settlement is possible on our behalf," Maxwell said, adding he was encouraged with the jury's decision.