White House Chief of Staff John Sununu's office on Friday blamed a billing mix-up for his late reimbursements for personal travel on military aircraft.

The bills were up to eight months old before Sununu paid them in a lump sum of $3,768 in July.An aide said the delay occurred because the bills were not sent to Sununu's office, apparently due to staff changes in the White House military office.

"There was clearly something wrong. The bills hadn't been paid," until Sununu's secretary, Jackie Kennedy, noticed the problem, said the aide, who spoke on the condition of anonymity.

Bills sent to others who flew with Sununu were paid promptly, according to The Washington Post, which disclosed Sununu's delinquency in Friday's editions.

Nearly all of Sununu's personal travel bills were paid from a political fund left from his days as governor of New Hampshire, a legal use of the money.

"There was money in the campaign fund all along," so there is no reason to think Sununu did not have the money to pay, the aide said.

The Post quoted an associate White House counsel, Gregory S. Walden, as saying he had not heard a satisfactory explanation for the delay in payment for six or seven trips by Sununu.