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 Thursday 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.