The Federal Reserve left a key short-term interest rate at a 45-year low but dropped a promise it had been making since last August to keep rates low "for a considerable period."

　　The wording change was enough to jolt financial markets on Wednesday, sending stock prices plunging, even though private economists said they believed the Fed still planned on keeping rates unchanged for most of this year.

　　The Dow Jones industrial average, which had been in positive territory before the Fed's afternoon announcement, ended the day down 141.55 points at 10,468.37, a 1.3 percent drop which erased nearly all of the Dow's gains since the beginning of the year.

　　Bond prices dropped, too, sending interest rates higher. The yield on Treasury's 10-year note climbed to 4.19 percent, up from 4.08 percent the previous day.

　　The adverse market reaction occurred because the Fed dropped the phrase it had included in its last four policy statements - that it believed low inflation and slack utilization of resources gave it the leeway to keep rates low "for a considerable period."

　　Instead, the central bank, still citing the low inflation and slack resource utilization, said it believed "it can be patient" before raising rates.

　　While the wording change was subtle, Wall Street worried that by dropping the phrase "for a considerable period," the central bank is getting closer to beginning a series of rate hikes to make sure the rebounding economy does not trigger inflation.

　　Still, private economists said the statement does not indicate a rate hike.

　　"The Fed is getting the market ready for tighter monetary policy eventually, but they are not going to raise interest rates any time soon," said Sung Won Sohn, chief economist at Wells Fargo in Minneapolis.

　　Complicating the issue this year is the presidential election. The central bank usually tries to avoid changing rates too close to the November vote out of concern that it could be seen as trying to favor one party over the other.

　　For that reason, many economists said they still believe the central bank will stay on hold until after voters go to the polls in November.

　　"We have a slight change in wording, but I don't think there will be any change in policy until after the election," said David Jones, head of DMJ Advisors, an economic consulting firm. "The Fed is not going to act anytime soon to hike interest rates with inflation low and the unemployment rate still high."

　　The Fed last raised rates in June 2000, when it hiked the federal funds rate by a half-point to 6.5 percent, the last in a series of six rate increases the central bank had begun in June 1999.

　　Those rate hikes did slow economic growth, but they also contributed to a bursting of the stock market bubble in early 2000. The fallout pushed the country into a recession in March 2001, ending a 10-year economic expansion, the longest in US history.

　　Seeking to combat the growing economic weakness, the Fed started in January 2001 to cut interest rates in a series of moves that picked up momentum after the September 11, 2001, terrorist attacks, making 2002 the most aggressive period of rate cuts since Federal Reserve Chairman Alan Greenspan took the top Fed job in 1987.

　　Most of the rate cuts occurred in 2001, although 2002 saw a half-point cut and a quarter-point cut. That reduction last June pushed the funds rate down to 1 percent, the lowest it has been since Dwight Eisenhower was president.