Mr. Bush’s “shot in the arm,” economists said, did not persuade the rest of the world that the United States will escape a recession, or that it will either.

A decade after a credit crisis in Southeast Asia triggered an “Asian contagion” of stock market declines around the world, the credit crisis in the United States is now producing an “American contagion” to which no stock market seems immune.

“There is indeed some panic,” said Thomas Mayer, the chief European economist at Deutsche Bank in London.

The Japanese stock market dropped 5.7 percent, for the worst two-day loss in 17 years, while the Australian stock market tumbled 7.05 percent, its worst single-day loss in nearly two decades. The Shanghai market lost 7.22 percent while the Hang Seng index in Hong Kong plummeted 8.65 percent.

European stock indexes opened with losses of 2 to 5 percent, extending a steep slump that pushed some indexes down more than 7 percent on Monday.

Trading on the Bombay Stock Exchange was halted for an hour on Tuesday after the Sensex index dropped 11.5 percent shortly after the opening.

On Monday, the Frankfurt Stock Exchange’s Dax index plummeted 7.2 percent, its steepest one-day decline since Sept. 11, 2001. The 7.4 percent drop in Bombay’s Sensex index was the second-worst single-day tumble in its history.