GLOBAL MARKETS-Stocks rise, gold tumbles; U.S. bank shares up

* Markets await Bernanke speech

* Gold tumbles another day

* World stocks up slightly, U.S. stocks open higher (Updates with U.S. market open, changes dateline, previous LONDON)

NEW YORK, Aug 25 (Reuters) - Gold fell for a third day on Thursday, while world stocks edged higher as investors tried to anticipate what the Federal Reserve chairman may signal at a speech this week.

U.S. stocks opened higher, with shares of Bank of America jumping more than 25 percent to $8.76 after Berkshire Hathaway said it would invest $5 billion in the bank. Other financial shares also shot higher, including Citigroup , up 10.4 percent at $31.38, and the S&P financial index <.GSPF> up 4.4 percent. For details, see [ID:nWNAB2425]

Fed chief Ben Bernanke is due to address central bankers at an annual symposium in Jackson Hole, Wyoming, on Friday. His speech last year laid the groundwork for the Fed's $600 billion bond-buying program to revive a sputtering U.S. economy under a policy that was termed the second round of quantitative easing.

While many doubt Bernanke will immediately commit to conducting a third round of quantitative easing, investors generally expect him to stress that the central bank stands ready to act if necessary.

Markets have been volatile in the past month because of concern over whether the U.S. economy is headed for another recession and how far the euro zone debt crisis may spread.

Stocks have had a rebound this week after four weeks of losses. The MSCI world equity index <.MIWD00000PUS> rose 0.4 percent. The benchmark index is on track to post its first weekly gain in five weeks, having hit an 11-month low earlier this month.

On Wall Street, the Dow Jones industrial average <.DJI> was up 65.96 points, or 0.58 percent, at 11,386.67. The Standard & Poor's 500 Index <.SPX> was up 10.20 points, or 0.87 percent, at 1,187.80. The Nasdaq Composite Index <.IXIC> was up 9.42 points, or 0.38 percent, at 2,477.11.

GOLD DROPS

Gold extended its sharp decline, after posting its biggest daily drop in futures since 1980 on Wednesday. Spot gold was down 2.2 percent at $1,711.99 an ounce. It hit a record high of $1,911.46 earlier in the week.

The fall came after CME Group raised trading margins on bullion futures by about 27 percent, the biggest hike in more than two and a half years and the second increase in a month.

Gold prices had jumped about $400 since July as worries about a global recession sent investors scrambling for the safe-haven asset.

European stocks <.FTEU3> added 0.3 percent, while the dollar <.DXY> dipped 0.1 percent against a basket of major currencies. (Reporting by Caroline Valetkevitch in New York and Natsuko Waki in London; Editing by W Simon )