WASHINGTON — In good news for home buyers, rates on 30-year mortgages fell below the 6 percent level this week for the first time in three months, although economists said they don’t expect rates to stay at this level for long.

Freddie Mac said Thursday in its weekly nationwide survey that rates on 30-year, fixed-rate mortgages fell to 5.98 percent percent this week, down from 6 percent last week. The rate was the lowest since the last time the 30-year mortgage was below 6 percent on April 22, when rates averaged 5.94 percent.

Since peaking at a high for this year of 6.34 percent the week of May 13, 30-year mortgage rates have been headed lower, reflecting in part a slowdown in economic activity in June.

The economy hit what Federal Reserve Chairman Alan Greenspan on Tuesday termed a “soft patch” in June. Greenspan, however, in delivering the Fed’s mid-year economic forecast to Congress, sought to allay fears that the slowdown could threaten the sustainability of the current recovery.

The Freddie Mac survey found that rates on 15-year, fixed-rate mortgages, a popular option for refinancing, edged down to 5.39 percent this week, the lowest level since late April and down from 5.40 percent last week.

Rates on one-year adjustable rate mortgages rose this week to 4.12 percent, up from 4.02 percent last week.