WASHINGTON — Rates on 30-year mortgages climbed this week to their highest point in nearly four years, a development that could put a further crimp in housing activity.

The Federal Home Loan Mortgage Corp., commonly known as Freddie Mac, reported yesterday that rates on 30-year, fixed-rate mortgages averaged 6.49 percent for the week ending April 13. That was up from 6.43 percent last week and was the highest since mid-July of 2002.

There are signs that rising mortgage rates are slowing the housing market, which registered record-high sales for five years in a row. Sales of existing homes are expected to fall by 6 percent this year compared with last year, while new-home sales are expected to drop by 10.9 percent, according to the National Association of Realtors.

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 averaged 6.14 percent this week, up from 6.10 percent last week. One-year adjustable rate mortgages increased to 5.61 percent, compared with last week's 5.57 percent. Rates on five-year, hybrid adjustable-rate mortgages averaged 6.13 percent, up from 6.11 percent.

The rates do not include add-on fees known as points. Thirty-year mortgages carried an average nationwide fee of 0.6 point; 15-year mortgages, 0.5 point; one-year ARMs, 0.8 point; and five-year ARMs, 0.7 point.

A year ago, 30-year mortgages averaged 5.91 percent, 15-year mortgages stood at 5.46 percent, one-year ARMs were at 4.30 percent, and five-year ARMs averaged 5.31 percent.