NEW YORK (AP) -- Average interest rates on most types of credit cards rose slightly this week, according to a report from CreditCards.com.

Annual percentage rates on seven out of nine categories of cards -- business, instant approval, airline, balance transfer, low interest, cash back and reward cards -- all rose slightly from the previous week.

Only two categories of cards didn't increase, according to the weekly report issued Thursday. The APR on cards for people with bad credit held steady at 10.82 percent while rates on student cards dropped slightly to 13.9 percent, down from 14.02 percent.

The across the board increases were largely the result of sharp hikes in rates for select American Express cards, said Ben Woolsey, spokesman for CreditCards.com, which tracks about 200 credit cards.

The hikes by American Express overshadowed some lowered APRs by major card issuers such as Citi and Chase, Woolsey said.  American Express Co. is expecting write-offs in its credit card portfolio to continue to mount in the fourth quarter and into next year as consumers struggle with a worsening economy.  Earlier this week, the company said it received government approval to become a bank holding company -- a sign the lender is facing difficulty funding its operations amid the credit crisis.