The Federal Reserve cut the target on a key short-term interest rate by a half of a percentage point Tuesday to 4.75%, further acknowledgment from the central bank that the mortgage meltdown plaguing Wall Street and Main Street could have a negative impact on the economy.

"This took some investors by surprise. It's like the Christmas present you really wanted but weren't really expecting," said Gary Webb, chief executive officer of Webb Financial Group, a Bloomington, Minn.-based independent investment advisory firm with about $120 million in assets under management.

The cut to the federal funds rate, the first since June 2003, was widely anticipated by investors and followed a surprise cut to the Fed's discount rate on Aug. 17. The only question was whether the Fed would lower the federal funds rate by 25 basis points or 50 basis points. (There are 100 basis points in a full percentage point.)

On Tuesday, the Fed also cut its discount rate by another half of a point to 5.25 percent. The central bank said that the vote to lower both rates was unanimous.

Some investors had thought that Fed chair Ben Bernanke would take a more cautious approach and not cut rates by such a large margin, because a half-point cut could signal the Fed was acting out of desperation to save the economy.

The federal funds rate, an overnight lending rate that banks charge each other, is important since it influences the amount of interest consumers must pay for various types of debt, such as credit cards, home equity lines of credit and auto loans. The rate cut should help some beleaguered home borrowers who are set to see monthly payments on adjustable rate mortgages rise later this year.

In its statement, the Fed said that "the tightening of credit conditions has the potential to intensify the housing correction and to restrain economic growth more generally" and that the rate cut "is intended to help forestall some of the adverse effects on the broader economy that might otherwise arise from the disruptions in financial markets and to promote moderate growth over time."