WASHINGTON — Rates on 30-year mortgages edged up slightly this week, posting the 10th consecutive increase and keeping rates at the highest level in more than two years.

Mortgage giant Freddie Mac reported yesterday that the U.S. average for 30-year fixed-rate mortgages rose to 6.37 percent, from last week's 6.36 percent.

Both weeks represented the highest levels since 30-year mortgages were at 6.44 percent in early September 2003.

The 30-year mortgage is now nearly a full percentage point above its low-point of this year of 5.53 percent set the week of June 30. But analysts said even with the increases the 30-year and adjustable-rate mortgages remain well below their averages over the past decade.

"It's good to keep in mind that current mortgage rates, overall, are still below the 1990s' averages of around 8 percent for a 30-year fixed-rate mortgage and 6 percent for the one-year ARM," said Frank Nothaft, chief economist at Freddie Mac.

The rising rates, however, are expected to cool off the booming housing market.

Rates on 15-year fixed-rate mortgages, a popular choice for refinancing a home mortgage, averaged 5.90 percent this week, up from 5.89 percent last week.

One-year adjustable rate mortgages rose to 5.20 percent, up from 5.12 percent, last week. Meanwhile, rates on five-year hybrid adjustable-rate mortgages averaged 5.86 percent this week, up from 5.81 percent last week.

The nationwide averages for mortgage rates do not include add-on fees known as points. All categories of mortgages in the Freddie Mac survey carried a nationwide average fee of 0.6 point last week.

A year ago, 30-year mortgages averaged 5.74 percent, 15-year mortgages were at 5.15 percent and one-year ARMs averaged 4.17 percent. Freddie Mac does not have historical data on the five-year ARM, which it began tracking this year.