WASHINGTON — U.S. long-term mortgage rates rose this week amid optimism over prospects for the U.S. economy. Rates remain at historically low levels, however, as an incentive to prospective homebuyers.

Mortgage giant Freddie Mac said Thursday the average rate for a 30-year fixed-rate mortgage jumped to 3.75% from 3.69% last week. By contrast, the benchmark rate stood at 4.94% a year ago.

The average rate on a 15-year mortgage increased to 3.2% this week from 3.13% last week.

Federal Reserve Chairman Jerome Powell told Congress this week that the central bank remains optimistic about the U.S. economy, though it still faces risks from slower growth overseas and trade tensions. Powell underscored his view that the economy is likely to continue growing, with no reason to believe that the likelihood of a recession is "elevated."

The Fed, which cut its short-term interest rate two weeks ago, is likely to keep rates unchanged in the coming months, unless there was a "material" shift in the economy's outlook, Powell said.

The historically low home borrowing rates have sparked a homebuying rush. Mortgage applications, for both purchases and refinancing, rose 9.6% in the week ended Nov. 8 from a week earlier, according to the Mortgage Bankers Association.

Freddie Mac surveys lenders across the country between Monday and Wednesday each week to compile its mortgage rate figures.

The average doesn't include extra fees, known as points, which most borrowers must pay to get the lowest rates.

The average fee on 30-year fixed-rate mortgages increased to 0.6 point this week from 0.5 point. The average fee for the 15-year mortgage rose to 0.5 point from 0.4 point.

The average rate for five-year adjustable-rate mortgages rose to 3.44% from 3.39%. The fee rose to 0.4 point from 0.3 point.