* Global shares on track for biggest 1-day fall in 4 weeks
* Oil falls, commodities off record highs
* Yen up as investors unwind carry trades
By Wanfeng Zhou and Sebastian Tong
NEW YORK/LONDON, April 12 (Reuters) - Stocks on major markets slumped and some commodity prices fell from recent highs on Tuesday as concerns about economic growth and the impact of the nuclear crisis in Japan undermined investor confidence.
World stocks, as measured by the MSCI's main world equity index <.MIWD00000PUS> were down 0.8 percent by early New York trading, the index's biggest one-day decline in four weeks.
U.S. stocks slipped after a disappointing revenue reported
by aluminum maker Alcoa Inc
"There's been an undercurrent of selling in the market this last week. The tone appears to be becoming more negative. Risk levels appear to be rising," said Wayne Kaufman, chief market analyst at John Thomas Financial in New York.
The FTSEurofirst 300 index <.FTEU3> of top European shares slipped 1.3 percent, with miners and energy firms among the heaviest losers. Emerging markets <.MSCIEF>, which count several resource exporters in their ranks, fell 1.5 percent.
Brent crude oil
Societe Generale also said rising gasoline prices in the U.S. were fueling a debate about "demand destruction" in the world's top economy. "Geopolitics (are) still critical. But with prices high, markets may be having doubts on demand," SocGen said. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ For oil futures positions vs. oil price since 2007: http://r.reuters.com/duc98r
All Commodities Futures Trading Commission positions: http://r.reuters.com/buv87r ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Spot gold
SAFE-HAVEN DEMAND
Concerns over global growth were heightened after Japan's economic minister warned that the economic damage wrought by last month's earthquake and tsunami could be worse than initially thought. [ID:nL3E7FC092]
Japan's move to put the severity of radiation leakage at its stricken Fukushima nuclear plant on a par with the worst nuclear disaster at Chernobyl also weighed on sentiment. [ID:nL3E7FB2TZ]
The yen and Swiss franc rose as jittery investors sold riskier trades funded by borrowing in the two low-yielding currencies.
"Our positioning data shows some carry trades are pretty extended," said Chris Walker, currency strategist at UBS.
The yen firmed to a 1-1/2 week high versus the U.S. dollar
Still, the steadier yen offered the dollar some respite, allowing the greenback to stay above Friday's 16-month lows against a basket of major currencies <.DXY>.
Dovish comments from key U.S. Federal Reserve officials are likely to cap the greenback's gains.
Two of the Fed's most powerful officials, Janet Yellen and William Dudley, said the U.S. central bank should stick to its super-easy monetary policy as inflation was not a threat and unemployment remains too high. [ID:nN11296347] (Additional reporting by Angela Moon and Gertrude Chavez-Dreyfuss in New York, Neal Armstrong and Zaida Espana in London;)