WASHINGTON — The key long-term U.S. mortgage rate held steady this week, providing a lure for potential homebuyers as the spring buying season goes forward.

Mortgage buyer Freddie Mac said Thursday the average rate on 30-year, fixed-rate mortgages was 4.55 percent, unchanged from last week. The benchmark rate rose steadily for most of April, reaching its highest level in more than four years. By contrast, the rate averaged 4.05 percent a year ago. The average rate on 15-year, fixed-rate loans declined slightly to 4.01 percent from 4.03 percent last week.

Despite higher borrowing costs and home prices, demand has grown in the spring buying season as the economic outlook has continued to improve and bolstered consumer confidence.

Homes sold at a solid annual pace of 5.6 million in March, the National Association of Realtors reported last week, even though the number of houses for sale has plunged. As a result, average home prices are rising at more than twice the pace of wages.