* Weak reading of U.S. factory data takes steam out of equities
* Euro hits 6-week high vs dollar on Greek debt moves
* Crude trims gains after initial rise on upbeat data from China
* Spain seeks help for troubled banks; pulls Treasuries lower
By Herbert Lash
NEW YORK, Dec 3 (Reuters) - Global shares and crude oil pared early gains to trade lower on Monday after U.S. manufacturing activity hit a three-year low in November, offsetting signs of revived growth in China.
Wall Street opened higher, following gains in European equity markets, on upbeat factory data from China and a slower contraction in European manufacturing. But U.S. shares subsequently trimmed gains and fell.
The euro leaped to its highest level against the U.S. dollar in six weeks as concerns abated about debt-burdened Greece and Spain, while Chinese data allayed worries about global growth.
But concerns over budget dealings in Washington on the "fiscal cliff" remained the primary focus of investors. Unless Congress acts, some $600 billion of sharp spending cuts and tax hikes will take effect starting in January.
"At this point, all you can say about the data is they are discounting it," said Paul Mendelsohn, chief investment strategist at Windham Financial Services in Charlotte, Vermont. "So barring some catastrophe here in terms of the fiscal cliff, we look pretty stable."
In a sign U.S. manufacturing may be struggling to gain traction, the Institute for Supply Management said its index of national factory activity fell to 49.5 from 51.7 in October.
The figure was the softest since July 2009, when the U.S. economy was struggling in the aftermath of the financial crisis and may have been affected by superstorm Sandy, which hit the U.S. East Coast in late October.
The Dow Jones industrial average was down 50.33 points, or 0.39 percent, at 12,975.25. The Standard & Poor's 500 Index was down 4.88 points, or 0.34 percent, at 1,411.30. The Nasdaq Composite Index was down 5.12 points, or 0.17 percent, at 3,005.12.
European shares gave up most of their gains in a late sell-off, retreating from a 17-month high following release of the U.S. manufacturing data and on persistent concerns about the U.S. fiscal dispute.
The FTSEurofirst 300 index of top European shares closed up 0.16 percent at 1,121.15, after earlier rising to 1,128.65.
World shares as measured by MSCI's all-country equity index were off 0.03 percent at 332.55.
The euro was up 0.62 percent at $1.3064, while the U.S. dollar index fell 0.39 percent to 79.837.
Copper touched a six-week high on the promising data from China, the world's top metals consumer. But doubts about the soundness of the global economy put a lid on gains.
Benchmark copper on the London Metal Exchange hit $8,045 a tonne, the highest since Oct. 19, before receding to $8,015.50, up 0.26 percent.
U.S. Treasuries prices fell on news that Spain is seeking help for its troubled banks and the Chinese manufacturing data reduced safe-haven demand for less-risky government debt.
"You got the Spain news, which was expected, but it was still welcomed news for risky assets. You also had some pretty good Chinese data. The (bond) market is a little fatigued," said Jason Rogan, director of Treasuries trading at Guggenheim Partners in New York.
The benchmark 10-year U.S. Treasury note was down 5/32 in price to yield 1.6284 percent.
Oil rose above $112 per barrel, spurred by signs that growth is picking up in China, before trimming gains, with North Sea Brent turning negative.
Brent futures were off 37 cents at $110.86 per barrel. U.S. crude rose 6 cents to $88.97 per barrel.