The average long-term U.S. mortgage rate rose this week to its highest level since mid March, driving up borrowing costs for prospective homebuyers facing a housing market that’s constrained by a dearth of homes for sale, the Associated Press reported. Mortgage-buyer Freddie Mac said yesterday that the average rate on the benchmark 30-year home loan rose to 6.57% from 6.39% last week. The average rate a year ago was 5.10%. High rates can add hundreds of dollars a month in costs for homebuyers, limiting how much buyers can afford in a market that remains unaffordable to many Americans after years of soaring home prices and limited housing inventory. The median monthly payment listed on applications for home purchase loans in April rose to $2,112, up nearly 12% from a year ago and a 0.9% increase from March, the Mortgage Bankers Association said Thursday. The average rate on a 30-year home loan has risen two weeks in a row, echoing moves in the 10-year Treasury yield, which lenders use as a guide to pricing loans. The 10-year Treasury yield has been mostly rising of late, climbing to 3.79% in afternoon trading Thursday. Two weeks ago, it was at 3.39%. “The U.S. economy is showing continued resilience which, combined with debt-ceiling concerns, led to higher mortgage rates this week,” said Sam Khater, Freddie Mac’s chief economist. Jitters over the possibility that the government ends up defaulting on its debt could cause creditors to ask for higher interest rates on U.S. Treasury bonds, which could lead to a “significant increase” in borrowing costs, including mortgages, said Jiayi Xu, an economist at Realtor.com.