WASHINGTON – Fixed mortgage rates were mostly unchanged last week, inching up from their yearly lows.

The average rate on the 30-year fixed loan ticked up to 4.52 percent from 4.51 percent a week earlier, Freddie Mac said. It reached its yearly low of 4.49 percent several weeks ago.

The average rate on the 15-year fixed loan, popular for refinancing, nudged up to 3.66 percent from 3.65 percent, its low point for the year.

Mortgage rates typically track the yield on the 10-year Treasury note. Yields fall when prices rise. In the past two weeks , yields have been stable even though Congress and the Obama administration are less than two weeks away from a possible default on the government’s debt.

Low mortgage rates and depressed home prices have done little to revive the struggling housing market.

To calculate average mortgage rates, Freddie Mac collects rates from lenders across the country on Monday through Wednesday of each week. Rates often fluctuate significantly, even within a single day.

The average rate on a five-year adjustable-rate mortgage edged down to 3.27 percent from 3.29 percent a week earlier. A month ago, it hit 3.25 percent, its lowest level on records dating back to 2005. The average rate on the one-year adjustable loan rose to 2.97 percent from 2.95 percent. It hit a record low a week earlier.

The rates do not include extra fees known as points. One point is equal to 1 percent of the total loan amount.

The average fees for the 30-year loans were unchanged at 0.7, according to Freddie Mac’s survey. Average fees for the 15-year fixed loan rose to 0.7.