WASHINGTON — Rates on 30-year mortgages rose for a third straight week as investors viewed improving economic reports as a sign that the Federal Reserve will not quickly cut interest rates.

Mortgage giant Freddie Mac reported yesterday that 30-year fixed-rate mortgages averaged 6.18 percent this week. That was up from 6.13 percent last week. However, it was still well below the high point for this year, which was 6.80 percent back in July.

The increases in recent weeks came after a prolonged slide in rates that helped set the stage for a rebound in home sales.

The National Association of Realtors reported yesterday that sales of previously owned homes rose by 0.6 percent in November after a 0.5 percent October increase, the first consecutive monthly sales gains since the spring of 2005. That report followed news on Wednesday that new-home sales rose by 3.4 percent in November.

Other types of mortgage rates also showed increases this week.

Rates on 15-year fixed-rate mortgages, a popular choice for refinancing, rose to 5.93 percent, up from 5.89 percent last week. The mortgage rates do not include add-on fees known as points. Thirty-year and 15-year mortgages each carried a nationwide average fee of 0.4 point. Five-year ARMs had an average fee of 0.5 point, while one-year ARMs carried a fee of 0.6 point.

A year ago, rates on three-year mortgages stood at 6.22 percent, while 15-year mortgages were at 5.76 percent, five-year ARMs averaged 5.79 percent and one-year ARMs were at 5.15 percent.