WASHINGTON — Rates on 30-year mortgages rose this week to the highest level since the spring of 2002.

Freddie Mac, the mortgage company, reported yesterday that rates on 30-year, fixed-rate mortgages increased to a nationwide average of 6.80 percent, up from 6.74 percent last week.

The increase pushed 30-year rates to the highest level since they stood at 6.81 percent the week of May 24, 2002.

The lowest mortgage rates in four decades powered a boom in housing that pushed sales of both new and existing homes to record levels for five consecutive years. But sales have slowed this year as mortgage rates have been rising.

Rates on 15-year, fixed-rate mortgages rose to 6.41 percent, up from 6.37 percent last week.

Rates on one-year adjustable rate mortgages rose to 5.80 percent, up from 5.75 percent last week.

Rates on five-year adjustable-rate mortgages rose to 6.36 percent, up from 6.33 percent last week.

A year ago, 30-year mortgages averaged 5.73 percent, 15-year mortgages stood at 5.32 percent, one-year ARMs were at 4.42 percent and five-year ARMs averaged 5.26 percent.

The mortgage rates do not include add-on fees known as points.