WASHINGTON — Rates on 30-year mortgages dipped below 6 percent this week, their lowest level in five weeks.

Mortgage company Freddie Mac reported yesterday that 30-year fixed-rate mortgages averaged 5.98 percent this week, down from 6.01 percent last week.

Rates on 15-year fixed-rate mortgages fell to 5.55 percent, from 5.60 percent last week. But rates on one-year and five-year adjustable-rate mortgages rose.

The five-year adjustable-rate mortgage edged up to 5.61 percent from 5.57 percent last week. One-year ARMs rose to 5.24 percent, up from 5.18 percent.

Analysts said financial markets pushed longer-term rates down in response to continued weakness in the economy. But ARM rates rose because they are more sensitive to Federal Reserve actions on short-term rates, and the Fed is considered unlikely to cut rates further.