The Dow Jones industrial average closed below 10,000 for the first time in three months Monday on nagging concerns about debt loads in Europe.
Shares of big banks pulled the market lower, extending a slump that has led to four straight weekly losses.
Rising deficits in weaker European economies including Greece, Portugal and Spain have raised questions about the health of the global financial system.
Greece's finance minister said Monday the government is preparing to boost some taxes to shore up its finances. But civil servants opposed to cutbacks have pledged to strike on Wednesday.
The questions about finances in Europe are only the latest blow to investor confidence. The market began to stumble in mid-January after China announced plans to contain economic growth and as the Obama administration proposed rules to restrict trading by large financial institutions.
That interrupted a 10-month climb in stocks, which hit 12-year lows last March. The Dow is down 817 points, or 7.6 percent, since closing at a 15-month high of 10,725.43 on Jan. 19.
Brett Hryb, a portfolio manager with MFC Global Investment Management in Toronto, said the latest concern is that the financial troubles in a country like Greece, whose economy is small compared with the rest of Europe, will spill into other countries.
"Clearly Greece itself is nothing. It's just a blip. It's what the contagion could be," he said.
According to preliminary calculations, the Dow fell 103.84, or 1 percent, to 9,908.39. On Thursday, the Dow traded below the psychological barrier of 10,000 for the first time since November. It hadn't closed below that mark since Nov. 4, 2009.
The broader Standard & Poor's 500 index fell 9.45, or 0.9 percent, to 1,056.74, while the Nasdaq composite index fell 15.07, or 0.7 percent, to 2,126.05.
Bond prices were mixed. The yield on the benchmark 10-year Treasury note, which moves opposite its price, rose to 3.58 percent from 3.57 percent late Friday.
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