World stocks on major markets fell further as investors focused on whether the United States will tackle its fiscal problems, while the euro fell to a two-month low after the European Central Bank refrained from taking more action despite signs of further economic slowdown.
Despite US lawmakers' pledges to avoid the automatic tax rises and spending cuts due to start early next year, known as the "fiscal cliff", doubts persisted as to whether Congress can agree on a timely compromise.
Fears that the world's biggest economy may suffer a recession in 2013 as a result of the sudden fiscal austerity, worth $US600 billion, led to sharp falls stocks and crude oil prices on Wednesday.
"This gridlock adds to the uncertainty for markets. It shows the difficult problems Washington faces won't get fixed any time soon," said Daniel North, chief economist at Euler Hermes ACI in Owings Mills, Maryland.
However, US stocks stabilized Thursday morning partly on news of a rise in US exports and a bigger-than-expected drop in jobless benefit claims, though claims were distorted by the storm that disrupted life in US Northeast in the past week.
On Wall Street, the three major US stock indexes reversed their slight gain after a flat opening. Their decline accelerated in early afternoon trading, prompted by investors socking more money into bonds from stocks, analysts said.
The Dow Jones industrial average was down 68.57 points, or 0.53 per cent, at 12,864.16. The Standard & Poor's 500 Index was down 8.92 points, or 0.64 per cent, at 1,385.61. The Nasdaq Composite Index was down 23.81 points, or 0.81 per cent, at 2,913.47.
Whole Foods Market Inc reported income that matched forecasts, but shares of the biggest US natural and organic grocery chain fell 4.8 per cent to $US91.31.
On Wednesday, the S&P 500 stock index suffered its biggest one-day per centage drop since June, and the Dow closed at its lowest since early August.
The FTSE Eurofirst 300 index of top European shares closed down 0.15 per cent at 1,097.71 on Thursday, the lowest level in a week.
FTSE component Siemens ended up 1.8 per cent at 80.27 euros a share after the German engineering conglomerate reported a smaller-than-expected drop in profits and announced a cost-saving plan worth 6 billion euros ($US7.7 billion).
The MSCI world equity index was down 0.8 per cent at 324.20 after Tokyo's Nikkei lost 1.5 per cent.
The ECB left its key interest rate at 0.75 per cent, disappointing some traders who had bet on more policy easing in the wake of recent comments by ECB President Mario Draghi on the weak economic outlook and gloomy European Commission growth estimates.
The Bank of England left its key rate unchanged at 0.5 per cent.
The absence of more ECB action spurred selling in the euro , knocking it down to a two-month low versus the US dollar at $US1.2719. It last traded at $US1.2744, down 0.22 per cent for the day.
The euro had been under pressure before the ECB rate decision even though the Greek parliament approved in the early hours of Thursday an austerity package needed to unlock international aid and avert bankruptcy, defying political rifts and violent protests.
"The euro will continue to weaken because there is no recovery in sight for Europe and the rest of the world continues to slip," said Joseph Trevisani, chief market strategist at Worldwide Markets in Woodcliff Lake, New Jersey.
Meanwhile, Spain, another heavily indebted euro zone member, sold 4.8 billion euros ($US6 billion) of new debt, completing its cash needs for this year. This meant Madrid can hold out longer before asking for international aid.
The somewhat encouraging news in Europe curbed safe-haven bids for US and German government debt, but persistent unease about the region's debt woes and the gridlock in Washington deterred any meaningful selling in bonds.
The yield on the benchmark 10-year US Treasury note fell 6 basis points to 1.628 per cent after the strong 30-year bond auction, while German Bund futures were up 28 basis points at 143.02, nearly their session highs.
In commodity markets, crude oil retreated from its session highs after tumbling more than $US4 a barrel on Wednesday on concerns about weak demand for fuel as the US and European economies face the risk of a protracted slowdown.
Brent crude was flat at $US106.82 per barrel after falling nearly 4.0 per cent on Wednesday, its steepest drop since December 2011. It rose as high as $US108.17 earlier.
US crude rose 53 cents to $US84.95, after losing nearly 5 per cent in the previous session, also its biggest slump since December 2011.
Gold was on track for a fourth straight days of gains on safe-haven bids due to worries about the US fiscal cliff and Europe's debt crisis. Spot bullion was up 0.41 per cent at $US1,723.45 an ounce.