The U.S. stock market resisted joining a wave of global selling today until the final minutes of trading, when it quickly tumbled.

The Dow Jones industrial average, up more than 100 points this afternoon, closed down 203.18 points, or 2.4 percent.  The Standard & Poor's 500 index closed down 3.2 percent, while the Nasdaq composite index fell 3 percent.

Shares of producers of oil and raw materials were lower amid evidence of a global economic slowdown. Regional bank shares were strong on the back of a second wave of capital infusions from the Treasury Department. A report showing a September rise in sales of new homes appeared to buoy the market

In the end, however, was the recognition that none of the factors that have been driving the sell-off in global stocks this month has changed. Investors around the world have been dumping stocks. Hedge funds in particular are liquidating as the yen carry trade, borrowing in low-interest yen and investing in higher-yield markets, is being unwound.  In Tokyo, stocks fell 6.4 percent to its lowest close since October 1982. Hong Kong stocks tumbled 12.7 percent; Shanghai ended down 6.3 percent.  Stocks in Europe were down.

More governments, including Japan's and Belgium's, are moving to help shore up banks. Finance ministers of the Group of Seven nations expressed concern about the volatility of the yen, and the International Monetary Fund announced rescue plans for Hungary and Ukraine just days after detailing one for Iceland.

Investors may be focused this week on what governments do and on economic data coming out: The Federal Reserve is expected to cut its benchmark interest rate on Wednesday, and the first estimate of the U.S. economy's gross domestic product is released on Thursday. But there is also a pressure to sell in this market that will not be eased by any good news on the macroeconomic front.

The Financial Times' Alphaville blog points to a bearish note from Nomura Securities this morning:

"With markets behaving the way they are, rationalizing such extreme movements with economic or corporate fundamentals is virtually impossible. Risky financial assets have effectively ceased to be discounters of likely future economic events."