WASHINGTON (AP) - Rates on 30-year mortgages climbed above 6 percent this week for the first time in 2004 as more signs of an improving economy triggered concerns about what impact the stronger growth will have on inflation.

Rates on 30-year fixed-rate mortgages rose to 6.01 percent, marking the sixth consecutive weekly increase since rates hit a low for the year of 5.38 percent the week of March 18, Freddie Mac reported Thursday.

The mortgage giant's nationwide survey of rates showed that the increase, up from 5.94 percent last week, left 30-year mortgages at their highest level since they averaged 6.02 percent the week of Dec. 5.

"With financial markets more optimistic that the economy is expanding nicely, mortgage rates had no where to go but up this week," said Amy Crews Cutts, deputy chief economist at Freddie Mac.

She said at the moment investors are split between being encouraged about the economy's rebound and worried about what impact that could have on inflation and the Federal Reserve's interest rate decisions.

"Perhaps next week's Federal Reserve meeting and the release of the April employment numbers will help the market find a balance between the two influences," she said.

Rates for 15-year, fixed-rate mortgages climbed to 5.35 percent, up from 5.25 percent last week. It was the highest level for this popular option for refinancing since the week of Dec. 6.

For one-year adjustable rate mortgages, rates were 3.75 percent this week, up from 3.69 percent last week.