WASHINGTON — Rates on 30-year mortgages stayed above 6 percent for the third straight week, rising to the highest level in 15 months.

Mortgage giant Freddie Mac reported yesterday that the nationwide average for 30-year, fixed-rate mortgages rose this week to 6.15 percent, up from 6.10 percent last week and the highest level since 30-year mortgages were at 6.21 percent in late July 2004.

Rates on all other types of mortgages were up as well this week, reflecting growing nervousness in financial markets about inflation pressures, generated in part by the spike in energy prices in the wake of the lost production following the Gulf Coast hurricanes.

The nation's housing market has been booming this year with sales of new and existing homes expected to set records for the fifth consecutive year. However, economists say the sales pace will slow next year under the impact of higher mortgage rates.

The government reported yesterday that new home sales rose by 2.1 percent in September to a seasonally adjusted 1.22 million, but the median price of a new home fell by 5.7 percent to $215,700, indicating some cooling in demand.

"Although home sales were still impressive in September, mortgage applications in October seem to be tapering off a bit, due in large part to slowing rising interest rates," said Frank Nothaft, chief economist for Freddie Mac.

Rates on 15-year, fixed-rate mortgages, a popular choice for refinancing a home mortgage, averaged 5.69 percent this week, up from 5.65 percent last week.

One-year adjustable rate mortgages rose to 4.91 percent. This was up from 4.89 percent last week and pushed the one-year ARM to its highest level since the week ending April 26, 2002.

Rates on five-year hybrid adjustable rate mortgages averaged 5.63 percent this week, up from 5.59 percent last week.

The nationwide averages for mortgage rates do not include add-on fees known as points. The 30-year and 15-year mortgages both carried a nationwide average fee of 0.5 point while the five-year ARM had an average fee of 0.6 point and the one-year ARM had an average fee of 0.7 point.

A year ago, 30-year mortgages averaged 5.64 percent, 15-year mortgages were at 5.01 percent and one-year ARMs averaged 3.96 percent.