Montana State University has canceled a scheduled speech by the former Navy SEAL who says he killed Osama bin Laden after his arrest for driving under the influence.

The school says it will honor its contract and pay Rob O'Neill's $28,000 speaking fee.

The university cited "unforeseen circumstances" in canceling Monday's speech by O'Neill, who has said he killed bin Laden during a raid on his Abbottabad compound in May 2011. O'Neill was arrested for DUI in Butte early Friday, after he was found sleeping at the wheel of a running vehicle at a convenience store.

O'Neill pleaded not guilty to the misdemeanor charge. He released a statement saying he had taken a prescription sleep aid and had not been drinking.

MSU spokesman Tracy Ellig said anyone who bought tickets to O'Neill's speech would receive a refund.