WASHINGTON (AP) — Average long-term U.S. mortgage rates edged lower this week, with the key 30-year loan rate remaining under 4 percent.

Mortgage giant Freddie Mac said Thursday the average rate on a 30-year fixed-rate mortgage ticked down to 3.93 percent from 3.94 percent a week earlier. A year ago, the average rate was 4.10 percent.

The rate on 15-year fixed-rate mortgages eased this week to 3.15 percent from 3.17 percent.

Investors and financial experts are watching for an anticipated interest-rate increase by the Federal Reserve next month, which could bring higher rates for home loans. The Fed has kept its key short-term rate near zero since the financial crisis year 2008.

With mortgage rates at historically low levels and job growth steady, Americans stepped up their home-buying for a third straight month in July. Data issued Thursday by the National Association of Realtors showed home sales accelerating last month to the strongest pace in eight years.

The spike in home sales has come as more current homeowners have returned to the real estate market for an upgrade or to downsize as they approach retirement.

To calculate average mortgage rates, Freddie Mac surveys lenders across the country at the beginning of each week. The average doesn't include extra fees, known as points, which most borrowers must pay to get the lowest rates. One point equals 1 percent of the loan amount.

The average fee for a 30-year mortgage was unchanged from last week at 0.6 point. The fee for a 15-year loan also held steady at 0.6 point.

The average rate on five-year adjustable-rate mortgages rose to 2.94 percent from 2.93 percent; the fee remained at 0.5 point. The average rate on one-year ARMs was unchanged at 2.62 percent; the fee held at 0.3 point.