The average long-term U.S. mortgage rate ticked up this week to just below its high for the year, the latest sign that borrowing costs on home loans remain elevated relative to where they were before the war with Iran started.

The benchmark 30-year fixed rate mortgage rate rose to 6.52% from 6.48% last week, mortgage buyer Freddie Mac said Thursday. Despite the increase, the average rate remains below 6.84%, where it was a year ago.

When mortgage rates rise they can add hundreds of dollars a month in costs for borrowers, reducing their purchasing power.

Mortgage rates are influenced by several factors, from the Federal Reserve’s interest rate policy decisions to bond market investors’ expectations for the economy and inflation. They generally follow the trajectory of the 10-year Treasury yield, which lenders use as a guide to pricing home loans.

Rates have been mostly trending higher since the conflict between the U.S. and Iran began in late February, disrupting the flow of crude oil from the Persian Gulf to customers worldwide. That’s sent oil prices sharply higher, helping drive up inflation.

Expectations of higher oil prices as the war drags on have kept long-term bond yields elevated, causing mortgage rates to mostly trend higher.

The yield on the U.S. 10-year Treasury note was at 4.53% in midday trading Thursday on the bond market, up from 4.47% a week ago. It was just 3.97% in late February, before the war broke out.