Gold prices dropped on Wednesday and were headed for their biggest two-day loss since the peak of the financial crisis, while the dollar rose as investors bet a speech by the Federal Reserve chairman later this week will not reveal any major central bank initiatives.

Even as investors pulled out of safe plays like government bonds and precious metals, world stocks edged lower.

U.S. stocks were volatile, seesawing between gains and losses on investor skepticism that the Fed can offer any new policy prescriptions that can help the economy. Both world and U.S. stocks rallied on Tuesday.

Markets have been in turmoil for the past month, weighing another possible U.S. economic recession and the impact of the euro zone debt crisis on the global economy. Benchmark stock indexes are on track for their worst month since the fall of 2008, after the Lehman Brothers collapse.

Investors have been hoping for additional action from the U.S. central bank to help.

The speech is a real wildcard for markets so people are being cautious, said Kathy Lien, head of research at GFT Forex in New York.

For gold investors, analysts said it's time to take money off the table after a safe-haven rally extended too far, too fast in recent weeks. Bullion was up by as much as $400 since July.

Spot gold was down 2.5 percent at $1,783.29 an ounce, off its session low of $1,762.90. On Tuesday, it dropped about 4 percent after an early rise to a record $1,911.46.

The dollar edged up, but traders said there was little conviction behind the gain, as reflected by several back-and-forth moves inside fairly tight ranges.

The dollar .DXY was last up 0.2 percent against a basket of currencies.

Speculation is widespread in financial markets that Fed chief Ben Bernanke will use his Friday speech at a central banker conference in Jackson Hole, Wyoming, to signal a new monetary offensive to support the faltering U.S. economy.

However, many analysts think Bernanke is most likely to outline gradualist measures, which would disappoint those looking for a big bang approach such as a fresh round of bond buying, or QE3.

I think some of the dollar buying is based on the idea that (Fed Chairman Ben) Bernanke won't be too aggressive just yet, Lien said.

UPBEAT U.S. DATA

Stock investors initially tried to build on positive sentiment after weeks of selling.

Supportive for some markets was data showing better-than-expected U.S. durable goods orders, as well as a U.S. Congressional Budget Office prediction of a decline in the deficit in coming years as a result of the government's recent debt-reduction agreement.

World stocks as measured by MSCI .MIWD00000PUS were down 0.1 percent on the day.

On Wall Street, the Dow Jones industrial average .DJI was down 21.95 points, or 0.20 percent, at 11,154.81. The Standard & Poor's 500 Index .SPX was down 2.58 points, or 0.22 percent, at 1,159.77. The Nasdaq Composite Index .IXIC was down 17.00 points, or 0.69 percent, at 2,429.06.

The FTSEurofirst 300 index .FTEU3 of top European shares gained for a third straight session and provisionally finished 1.3 percent stronger at 935.76, while Japanese shares sold off following Moody's Investors Service's downgrade of the country's sovereign debt.

Tokyo's Nikkei average .N225 closed down more than 1 percent. Overseas investors in particular reacted negatively to the downgrade.

Oil prices gained, while the benchmark 10-year Treasury note was last down 15/32 in price and yielding 2.21 percent, up from 2.16 percent late on Tuesday.

(Reporting by Caroline Valetkevitch, with additional reporting by Jan Harvey in London and Frank Tang, Ryan Vlastelica and Steven Johnson in New York; Editing by Dan Grebler)