WASHINGTON » Average U.S. rates for fixed mortgages barely changed this week, hovering near historically low levels.

Mortgage buyer Freddie Mac says the average for the 30-year loan slipped to 4.51 percent from 4.53 percent last week. The average for the 15-year loan edged up to 3.56 percent from 3.55 percent.

Mortgage rates have risen more than a full percentage point since hitting record lows a year ago. The increase was driven by speculation that the Federal Reserve would reduce its $85 billion a month in bond purchases.

Last month, the Fed determined the economy was strong enough to start cutting those monthly purchases by $10 billion. The bond purchases have kept long-term interest rates low.

The rise in mortgage rates has slowed home sales, which have fallen for three straight months.