The average long-term U.S. mortgage rate climbed this week to its highest level in more than 20 years, grim news for would-be homebuyers already challenged by a housing market that remains competitive due to a dearth of homes for sale.

Mortgage buyer Freddie Mac said Thursday that the average rate on the benchmark 30-year home loan rose to 7.09 percent from 6.96 percent last week. A year ago, the rate averaged 5.13 percent.

It’s the fourth consecutive weekly increase for the average rate and the highest since early April 2002, when it averaged 7.13 percent. The last time the average rate was above 7 percent was last November, when it stood at 7.08 percent.

High rates can add hundreds of dollars a month in costs for borrowers, limiting how much they can afford in a market already unaffordable to many Americans.

“With prices even higher than they were a year ago in many markets, crossing the 7 percent mortgage rate threshold again could be what sets in motion a major contraction in the housing market this fall,” said Lisa Sturtevant, chief economist for Bright MLS.

The latest increase in rates follows a sharp uptick in the 10-year Treasury yield, which has been above 4 percent this month and climbing. The yield, which lenders use to price rates on mortgages and other loans, touched its highest level since October on Thursday morning.