WASHINGTON — Rates on 30-year mortgages climbed this week, hitting their highest point in nearly four years, a development that will be weighed by people thinking about buying a home or refinancing the one they own.

Freddie Mac, the mortgage company, reported yesterday that for the week ending May 4, rates on 30-year fixed-rate mortgages averaged 6.59 percent, up slightly from 6.58 percent last week.

This week's rate was the highest since the week ending June 20, 2002, when 30-year mortgage rates stood at 6.63 percent.

It marked the sixth week in a row that rates on 30-year mortgages went up. These rates have been rising as Wall Street investors have worried about inflation picking up.

"We expect that the mortgage rates will continue to trend upward over the coming year but that upward trend will be modest at best," said Frank Nothaft, Freddie Mac's chief economist.

Even so, higher rates will affect people's appetite to refinance their home mortgage, he said.

"Fewer families will be refinancing; but of those who are, a larger percentage will be drawing some equity out of their homes, many to pay off previously existing home-equity loans and lines of credit as these loans become more expensive," Nothaft predicted.

Rates on 15-year, fixed-rate mortgages, a popular choice for refinancing a home mortgage, also edged up this week to 6.22 percent, from 6.21 percent last week.

However, one-year adjustable rate mortgages dipped to 5.67 percent this week, down from 5.68 percent last week. Rates on five-year, hybrid adjustable-rate mortgages averaged 6.21 percent this week, unchanged from last week.

The mortgage rates do not include add-on fees known as points. Thirty-year and 15-year mortgages each carried an average nationwide fee of 0.6 point. One-year ARMs carried a fee of 0.8 point and five-year ARMs had a fee of 0.7 point.

A year ago, 30-year mortgages averaged 5.75 percent, 15-year mortgages stood at 5.31 percent, one-year ARMs were at 4.22 percent and five-year ARMs averaged 5.16 percent.

Higher mortgage rates are expected to slow home sales this year. For five years running, home sales have hit record highs, powered by low mortgage rates.