* U.S. stocks slide as economic data curbs optimism
* S&P lower outlook for UK stirs fears about U.S. debt
* German bunds shine as gilts wilt after S&P action
* Dollar slumps, sterling falls, then rises on S&P
* Oil falls below $61 after rise to 6-month peak (Updates with U.S. markets activity; changes dateline, previous LONDON)
By Herbert Lash
NEW YORK, May 21 (Reuters) - Global stocks slid, the dollar fell and U.S. government debt plunged on Thursday as fresh signs of economic weakness and a potential credit rating cut for Britain dashed budding hopes for a quick recovery.
U.S. Treasuries debt fell sharply after the government said it would sell $101 billion of new notes next week, adding to worries whether global investors can digest all the pending supply.
Bond investors were also left mulling the value of U.S. debt after Standard & Poor's cut its credit outlook on the United Kingdom to negative from stable.
The weakness in government debt came despite a host of events that normally would be bullish for bonds, including falling stocks, the Federal Reserve buying Treasuries and data hinting the U.S. recession may be far from over.
At the same time analysts said an acceleration the dollar's slide this week may mark a pivotal moment in the financial crisis. A breakdown in the high correlation between the dollar and stocks hints at the return of stress-free investment patterns.
S&P's decision to cut its UK credit outlook to negative from stable threatened Britain's top AAA rating, and led some investors fear that huge deficits may leave the United States in the same situation.
"People are asking, if the UK is having problems like this then maybe U.S. sovereign debt is also not as solid," said David Dietze, chief investment strategist at Point View Financial Services in Summit, New Jersey, who noted, "there is going to be a huge amount of supply to feed the deficit."
Bill Gross, the co-chief investment officer of leading bond fund Pacific Investment Management Co., said market fears that the United States is at risk of losing its AAA credit rating was putting the U.S. dollar, stocks and bonds under severe selling pressure.
Investors fear that that United States is "going the way of the UK -- losing AAA rating which affects all financial assets and the dollar," Gross told Reuters via email.
The euro rose to a session peak of $1.3901, while the pound hit a session high at $1.5883 <GBP=> after earlier tumbling on S&P's potential downgrade of Britain's AAA credit rating.
S&P's action further weighed on investor sentiment after a disappointing regional Federal Reserve survey fueled doubts about the prospects for recovery. For details, see [
]The Philadelphia Federal Reserve Bank said its business activity index improved to minus 22.6 in May versus minus 24.4 in April -- but still weaker than economists' expectations of minus 18.0.
"The issue is, yes, we're moving higher, but we're still far short of what would classify as growth," said Dan Greenhaus, analyst at Miller Tabak & Co in New York.
Peter Kenny, managing director at Knight Equity Markets in Jersey City, New Jersey, said the data did not "justify the move we've seen in the Dow over the last two-and-a-half months."
"What it really is telling us is that we're in for a very slow and deliberate turn before we can really start building a solid foundation for the next move up in the market," he said.
Shares of big manufacturers dropped, and investors also pummeled technology shares.
At 1:30 p.m., the Dow Jones industrial average <
> was down 155.63 points, or 1.85 percent, at 8,266.41. The Standard & Poor's 500 Index <.SPX> was down 17.72 points, or 1.96 percent, at 885.75. The Nasdaq Composite Index < > was down 38.62 points, or 2.24 percent, at 1,689.22.European shares fell, weighed by banks and commodities, as S&P's potential UK credit cut added to worries sparked by news on Wednesday that Federal Reserve policy-makers had cut their U.S. growth forecasts over the next three years.
The pan-European FTSEurofirst 300 <
> index of top shares fell 2.1 percent to 857.52 points, breaking five successive sessions of gains."This is just a general pull-back by investors," said Peter Dixon, strategist at Commerzbank. "This is a sharp fall, but really it is a pause in what has been a remarkably strong rally."
Benchmark euro zone government bond rallied, outperforming UK gilts as well as higher yielding regional peers, after S&P's credit rating outlook for Britain.
The move sparked fears that S&P may take another look at ratings within the euro zone, said Calyon strategist Peter Chatwell, driving investors to the relatively safety of benchmark German Bunds.
"It looks as if the assumption is: Germany's safe ... the other issuers in the euro zone are maybe in doubt," Chatwell said.
Benchmark 10-year Treasury notes <US10YT=RR> were trading 33/32 lower in price to yield 3.31 percent, marking the highest yield in nearly two weeks. The 30-year bond <US30YT=RR> was trading 2-2/32 lower to yield 4.27 percent.
The dollar fell against a basket of major currencies, with the U.S. Dollar Index <.DXY> down 0.64 percent at 80.673. Against the yen, the dollar <JPY=> fell 0.37 percent at 94.50.
Oil fell below $61 a barrel, a day after hitting a six-month peak over $62. U.S. light sweet crude oil <CLc1> fell $1.16 to $60.88 a barrel.
Spot gold prices <XAU=> rose $12.20 to $949.30 an ounce.
Asian stocks slipped overnight on the Fed's lowered growth forecasts. Japan's Nikkei average <
> fell 0.9 percent as the yen strengthened and MSCI's index of Asian shares outside Japan <.MIAPJ0000PUS> eased 0.5 percent. (Reporting by Chuck Mikolajczak, Wanfeng Zhou and Chris Reese in New York; Joanne Frearson, Ian Chua, Catherine Bosley, Jane Merriman and Jan Harvey in London; writing by Herbert Lash; Editing by Leslie Adler)