Global share prices and the euro held steady on Wednesday as investors waited to see if central banks in the United States and Europe would take fresh actions to ease the euro-zone debt crisis and rejuvenate the global economy.

U.S. stocks pared early gains after unusual trading that roiled seemingly unrelated shares on the New York Stock Exchange raised concerns.

The Federal Reserve, which concludes its two-day policy meeting later in the day, is likely to show it is ready to act to support a weakening U.S. economy but stop short of aggressive measures for now.

The Fed's policy decision will come a day before a key meeting of the European Central Bank. ECB President Mario Draghi heightened speculation of further bank purchases of Italian and Spanish bonds when he said last week that he would do "whatever it takes to preserve the euro."

The risk of disappointment, however, is high. Spanish bond yields could jump again and stocks and the euro could sell off if the ECB does not deliver. Uncertainty ahead of the ECB meeting drove investors to safe-haven German bonds, allowing Berlin to sell five-year debt at a record low cost.

"Everybody is waiting on central bank policy. Right now the equity markets are being held together by easy money, and if we don't get more of it soon we are likely to be disappointed," said Jack Ablin, chief investment officer at Harris Private Bank in Chicago.

"We are going to need a monetary booster shot both from Europe and the U.S. to keep this party going."

The MSCI world equity index .MIWD00000PUS rose 0.1 percent to 316.40 points. European shares .FTEU3 gained 0.5 percent to 1,068.05.

But on Wall Street, traders appeared more concerned with unusually volatile trading in a number of shares listed on the NYSE, which resulted in the halt of several stocks that appear to be unrelated.

"I think that has disrupted all the normal activities. Stocks are moving all over the place, they are weird, they are trading like millions of shares, 100 shares at a time, so something went haywire somewhere," said Stephen Massocca, managing director at Wedbush Morgan in San Francisco.

The trading sparked unusual activity in stocks such as Molycorp (MCP.N), which traded more than 5.7 million shares in the first 45 minutes of trading. The stock usually averages about 2.65 million shares daily, and it was one of the stocks halted due to excessive volatility.

The Dow Jones industrial average .DJI was up 43.29 points, or 0.33 percent, at 13,051.97. The Standard & Poor's 500 Index .SPX was up 4.23 points, or 0.31 percent, at 1,383.55. The Nasdaq Composite Index .IXIC was up 4.26 points, or 0.14 percent, at 2,943.78.


Investors shrugged off economic data on the U.S. labor market and manufacturing activity worldwide.

The U.S. private sector added 163,000 new jobs in July, topping economists' expectations of 120,000 new jobs. The report from payrolls processor ADP came two days ahead of Friday's more important government monthly, non-farm payrolls report.

Also on Wednesday, surveys showed U.S. and euro zone factory activity struggled again in July while Chinese manufacturing fell to an eight-month low, as economies around the world showed signs of slowing.

"The manufacturing numbers are pretty dismal. There's really no good way to read them," said Omer Esiner, chief market analyst at Commonwealth Foreign Exchange in Washington. "I think they bolster the case for more Federal Reserve action, and globally, the argument is pretty much the same."

The malaise was worst in the 17-country euro zone, where output plummeted and the manufacturing sector contracted for an 11th straight month in July as a downturn that began in smaller countries continued to spread into core economies.

The euro slipped 0.1 percent to $1.2297.

Bundesbank President Jens Weidmann said in an interview published on the bank's website that governments overestimated the central bank's capacities and placed too many demands on it. He did not spell out whether he was referring to the Bundesbank or the ECB, though he was talking about the euro zone.

"On the ECB, the uncertainty is very high," said Jens Nordvig, global head of FX strategy at Nomura Securities in New York. "Some additional commitment to support sovereign bond markets is highly likely, but how firm and how conditional this commitment will be is far from clear."

In government debt trading, the benchmark 10-year U.S. Treasury note was down 11/32 in price, with the yield at 1.5052 percent.

Brent and U.S. crude futures rose after a report from the Energy Information Administration showed U.S. crude stocks fell 6.52 million barrels last week, much more than expected, as imports plunged.

Brent September crude was up $1.16 at $106.08 a barrel. U.S. September crude was up 82 cents at $88.88 a barrel.

Spot gold was down 1 percent at $1,597.04 an ounce.