WASHINGTON — Rates on 30-year mortgages marched up this week to their highest point in nearly four years, a factor that is taking some oomph out of the housing market.

Freddie Mac, the mortgage company, reported yesterday that for the week ending April 20, rates on 30-year, fixed-rate mortgages averaged 6.53 percent, up from 6.49 percent last week.

This week's rate was the highest since the week ending July 12, 2002, when 30-year mortgage rates stood at 6.54 percent.

Mortgage rates rose as Wall Street investors fretted that inflation might pick up, analysts said. These worries were fanned by government reports released earlier this week showing big increases in both wholesale and consumer prices for March.

Rising mortgages rates are crimping home sales and residential construction.

"As a result of higher mortgage rates, housing market activity is beginning to slow," said Frank Nothaft, Freddie Mac's chief economist.

The housing sector racked up record-high sales five years running. Sales, however, are expected to drop this year.

And, home prices, which have posted double-digit gains in past years, aren't expected to go up nearly as much this year.

Rates on 15-year, fixed-rate mortgages, a popular choice for refinancing a home mortgage, climbed to 6.17 percent this week, from 6.14 percent last week.

One-year adjustable rate mortgages increased to 5.63 percent this week, up from last week's 5.61 percent. Rates on five-year, hybrid adjustable-rate mortgages averaged 6.16 percent this week, up from 6.13 percent last week.

The mortgage rates do not include add-on fees known as points. Thirty-year mortgages carried an average nationwide fee of 0.6 point. Fifteen-year mortgages had a fee of 0.5 point, one-year ARMs carried a fee of 0.9 point and five-year ARMs had a fee of 0.8 point.