WASHINGTON — Mortgage rates rose this week with 30-year mortgages climbing to the highest level in more than four years on investor fears about inflation.

Freddie Mac, the mortgage company, reported yesterday that rates on 30-year, fixed-rate mortgages rose to a nationwide average of 6.71 percent, up from 6.63 percent last week.

It's the highest level for 30-year mortgages since they averaged 6.76 the week of May 31, 2002.

The housing sector is slowing this year under the impact of rising mortgage rates after five boom years powered by the lowest mortgage rates in four decades. Analysts predict that sales of new and existing homes will decline by more than 10 percent as higher mortgage rates make home ownership more costly.

A variety of mortgage types saw rates increase this week, gains that were attributed to growing worries about inflation and the likely reaction to those concerns at the Federal Reserve.

The Fed meets next week and financial markets now view it as a virtual certainty that the central bank will boost rates for a 17th consecutive time.

"Financial markets believe that the current rate of inflation is above the Fed's comfort zone, which will lead to more rate hikes in the near future," said Frank Nothaft, Freddie Mac's chief economist.

Rates on 15-year, fixed-rate mortgages, a popular choice for refinancing, increased this week to 6.36 percent, up from 6.25 percent last week.

Rates on one-year adjustable rate mortgages rose to 5.75 percent, up from 5.66 percent last week and the highest level since one-year ARMs averaged 5.77 percent the week of Aug. 3, 2001.

Rates on five-year adjustable rate mortgages climbed to 6.32 percent, up from 6.23 percent last week.

The mortgage rates do not include add-on fees called points. The 30-year and 15-year mortgages carried a nationwide average fee of 0.5 point, while the five-year ARM had an average fee of 0.6 point and the one-year ARM had an average fee of 0.8 point.

A year ago, 30-year mortgages averaged 5.57 percent, 15-year mortgages were 5.16 percent, one-year ARMs were 4.23 percent and five-year ARMs averaged 5.05 percent.