(Updates with stocks close)
By Richard Satran
NEW YORK, Jan 30 (Reuters) - Financial markets rallied on Wednesday in a brief celebration over a U.S. Federal Reserve interest rate cut that sent the Dow industrials 200 points higher before revived credit crunch fears erased the gains.
Bonds and the dollar moved lower as well.
Stocks leaped after the Fed's aggressive half-percentage-point rate cut to stimulate the sagging U.S. economy -- but quickly backed off as a jittery market reacted to speculation on financial television network CNBC that bond rating groups might cut bank insurers' ratings.
While no such announcement had been made, traders quickly booked profits since previous disclosures surrounding the insurers have hit markets hard. Bond insurers play a critical role in determining whether investors will purchase securities.
"My gut is telling me Moody's and S&P are going to downgrade either one or both," said the CNBC commentator.
The Dow Jones industrial average <
> closed down 37.47 points, or 0.30 percent, at 12,442.83. The Standard & Poor's 500 Index <.SPX> was down 6.49 points, or 0.48 percent, at 1,355.81. The Nasdaq Composite Index < > was down 9.06 points, or 0.38 percent, at 2,349.00. Earlier, the Dow had jumped as high as 12,680.The volatile trading followed the Fed's move, also aimed at stabilizing markets. Prior to the central bank's policy meeting, traders were evenly split over whether the Fed would cut rates by half a point or a quarter point.
Rate cut hopes rose early on Wednesday, on a report that U.S. economic growth last year dropped to a five-year low of 2.2 percent, with a fourth-quarter gain of just 0.6 percent, half the expected rate. The sluggish growth virtually assured a more aggressive move by the Fed, traders said.
"This move is really designed to help financial markets, even if it allows inflation pressures to pick up later on down the line," said Amo Sahota, president and head trader of global research at online foreign exchange compnay HiFX.
Inflation worries boosted gold to an all-time high above $940 an ounce and pushed bond prices lower. The benchmark 10-year U.S. Treasury note <US10YT=RR> was down 5/32, with the yield at 3.6992 percent. Bond yields rise as prices fall.
"The Treasury market's reaction tells you the long end of the market, contrary to what the Fed says, is really worried about inflation," said John Derrick, director of research and fixed-income securities manager at U.S. Global Investors Inc of San Antonio, Texas. "This is very aggressive action of 125 basis points of cuts in about a week."
The Fed set up expectations of an aggressive move after it made a 75 basis-point rate cut in an emergency action last week. The Fed has stepped up its operations to calm markets worried that investors pulling back from securities markets are causing a credit crunch, economists say.
Such fears were revived earlier in the day as European stocks opened lower when UBS AG <UBSN.VX> unveiled $4 billion in new write-downs. UBS was among the hardest-hit of the banks around the world that have collectively suffered more than $100 billion in losses from the crisis originating from defaults in U.S. subprime mortgages.
The big Swiss bank's charges reminded investors that the Fed action can do nothing to help results in the earnings season starting on Wall Street.
"The fourth-quarter reporting season will be a real acid test for the banks," said Franz Wenzel, strategist at AXA Investment Managers in Paris. Banks will use the opportunity to clear their books of bad loans, he said.
Investors betting that the bottom has already been reached in a U.S. recession drew support early in the session from a report from data provider ADP that 130,000 new U.S. private-sector jobs were created in January, three times the consensus forecast.
The Fed's rate cut revived the view that U.S. inflation could come back, especially with the dollar weaker and the economy stronger from rate cuts.
Gold on the New York futures market <GCJ8> rose $9.40, or 1 percent, to a record $940.20 before settling back to $934.
"The Fed understands that it needs to make hay while the sun shines by pumping as much liquidity into the economy now, while it still can, before the public's inflation expectations catch up with reality," said John Kosar, president of Asbury Research in Chicago.
The euro <EUR=> was up 0.69 percent at $1.4877 from a previous session close of $1.4775. Against the Japanese yen, the dollar <JPY=> was down 0.48 percent. (Reporting by Gertrude Chavez-Dreyfuss, Ellis Mnyandu and Pedro Nicolaci da Costa; Writing by Richard Satran; Editing by Jonathan Oatis)