Fixed mortgage rates were mostly unchanged this week as credit markets showed little reaction to Washington's impasse over raising the federal government's borrowing limit.

Freddie Mac reported Thursday that the average rate on the 30-year fixed loan ticked up to 4.55 percent from 4.52 percent a week ago. That's slightly above this year's low of 4.49 percent.

The average rate on the 15-year fixed loan was unchanged at 3.66 percent, just above the yearly low of 3.65 percent.

Mortgage rates typically track the yield on the 10-year Treasury note. Yields have been stable, even though Congress and the Obama administration are days away from a potential default on the government's debt.

Low mortgage rates and depressed home prices have done little to revive the struggling housing market. Many people simply can't take advantage of the historically low rates because of tighter lending standards and bigger required down payments.