Illinois financial officials say the U.S. credit-rating downgrade could mean lower investment returns and higher interest rates.

State Treasurer Dan Rutherford says investors were buying U.S. Treasury bonds Monday after Standard & Poor's declared the nation a higher risk for paying off its bills.

That drove down interest rates, part of Illinois' investment portfolio is in U.S. Treasury bonds. Rutherford says the downgrade will mean a lower return for Illinois.

Kelly Kraft is budget spokeswoman for Gov. Pat Quinn. She says it's possible the state could pay more interest on money it borrows this summer. But the state won't sell more bonds until September.

Kraft says that gives the market time to recover.