WASHINGTON — Mortgage rates shot up this week with 30-year mortgages climbing to the highest level in nearly a year, reflecting concerns in financial markets about the troubles at corporate giants Fannie Mae and Freddie Mac.

Freddie Mac reported Thursday that its nationwide survey showed rates on 30-year mortgages surged to 6.63 percent this week, up sharply from 6.26 percent last week. That represented the highest level for 30-year mortgages since they stood at 6.68 percent the week of Aug. 1.

Other mortgage rates showed similar hefty increases which analysts attributed to financial market jitters over rising mortgage losses at Fannie and Freddie.

Analysts said that the rising cost of funds for Fannie and Freddie had an immediate impact on the nationwide average for all mortgage rates since both companies are such big players. Fannie and Freddie either own or guarantee nearly half of the nation's mortgages.

The House on Wednesday approved and sent to the Senate legislation that would expand the government's powers to provide billions of dollars in loans.

and make direct purchases of Fannie and Freddie stock if necessary to shore up finances at the companies.

Supporters said the legislation, which also seeks to address a rising tide of mortgage foreclosures, should help arrest the worst slump in housing in a generation. President Bush has promised to sign it.

Mark Zandi, chief economist at Moody's