WASHINGTON — Rates on 30-year mortgages fell slightly this week to the lowest level since mid-July.

Freddie Mac, the mortgage company, reported Thursday that 30-year, fixed-rate mortgages dipped to 6.47 percent this week, down from 6.52 percent, which had been the rate for the previous three weeks. The new rate was the lowest since the week of July 17 when 30-year mortgages stood at 6.26 percent.

The 30-year mortgage has been above 6 percent since late May as financial markets have become convinced that rising inflation pressures will keep the Federal Reserve from cutting interest rates further even though the economy remains mired in a period of significant weakness.

The housing market continues in its worst slump in more than two decades. The government reported this week that construction of new homes fell in July to the slowest pace in more than 17 years, and the National Association of Home Builders said builder confidence remained at an all-time low in August.

Frank Nothaft, chief economist for Freddie Mac, said the industry will be watching next week when new figures are released on housing prices. They have been falling sharply over the past year as sellers struggle with slumping demand caused by the weak economy, tighter bank lending standards, and a glut of unsold homes caused by rising mortgage foreclosures.

The Freddie Mac survey showed other mortgage rates were mixed this week.

Rates on 15-year, fixed-rate mortgages, a popular choice for refinancing, fell to 6 percent, down from 6.07 percent last week.

Rates on five-year, adjustable-rate mortgages averaged 5.99 percent this week, down slightly from 6.02 percent last week.

However, rates on one-year, adjustable-rate mortgages bucked the downward trend, showing an increase to 5.29 percent, up from 5.18 percent last week.

The mortgage rates do not include add-on fees known as points. The nationwide average fee for 30-year mortgages and 15-year mortgages was 0.7 point. Five-year mortgages had an average fee of 0.6 point, while one-year mortgages carried an average fee of 0.5 point.

A year ago, rates on 30-year mortgages stood at 6.52 percent, 15-year mortgage rates averaged 6.18 percent, five-year adjustable-rate mortgages were at 6.34 percent, and one-year adjustable-rate mortgages stood at 5.60 percent.

California-based Realty Trac Inc. reported last week that the number of foreclosure filings jumped by more than 50 percent in July, while the National Association of Realtors said median home prices fell in three-fourths of the cities it surveyed in the April-June quarter.