WASHINGTON -- U.S. mortgage rates rose this week as the economy showed signs of strength, which makes it more likely that the Federal Reserve will raise its short-term rate next week.

The rate on the benchmark 30-year fixed-rate mortgage rose to 3.94 percent from 3.9 percent last week, mortgage giant Freddie Mac said. The 15-year, fixed-rate mortgage, popular among homeowners seeking to refinance, also increased, rising to 3.36 percent from 3.3 percent.

The five-year adjustable mortgage rate rose for the third straight week to 3.35 percent, from 3.32 percent last week.

Shorter-term rates are rising more quickly than longer-term debt, and the gap between the 30-year mortgage and five-year has narrowed since the summer. As a result, more homebuyers are choosing the longer-term fixed rate, Freddie Mac says.