NEW YORK (CNNMoney.com) - Mortgage rates rose higher this week after minutes from the Federal Reserve released Wednesday revealed some members are still concerned about rising inflation, Freddie Mac said Thursday.

The average rate on 30-year fixed-rate mortgages cranked up to 6.67 percent, for the week ending May 25, from the prior week's 6.62 percent. In the year-ago period, the 30-year mortgage rate averaged 5.62 percent.

The average rate hasn't been higher since June 2002, when it averaged 6.71 percent.

"The Fed released the minutes of its most recent meeting, which showed that some members were concerned about inflationary pressure. This caused the bond market yields to rise, and brought about market speculation that the Fed may hike rates sooner than had been expected," said Frank Nothaft, Freddie Mac vice president and chief economist.

"Higher mortgage rates will coincide with a cooling housing market. Although our forecast is for slightly higher rates, the rise will be gradual and orderly over the year."

The average rate on 15-year fixed-rate mortgages rose to 6.26 percent from 6.23 percent last week. A year ago, that loan averaged 5.20 percent.

Five-year adjustable-rate mortgages averaged 6.26 percent, up 0.05 from last week. The five-year ARM averaged 5.10 percent last year.

The average one-year adjustable-rate mortgage shot up to 5.68 percent from 5.61 percent. At this time last year, the one-year loan averaged 4.26 percent.

This week's numbers continue the trend of rising mortgage rates. For homeowners using adjustable rate mortgages (ARMs), a rise in interest rates can mean ballooning payments.

The Mortgage Bankers Association estimates that some $330 billion worth of ARMs will adjust in 2006 and $1 trillion worth will reset by the end of 2007. With a $200,000 loan adjusting upward from 4 percent to 6 percent, the monthly bill would increase to about $1,200, from $955.

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