The euro weakened about 1 percent against the dollar and the yen on Wednesday, one day before an important auction of long-dated Italian debt, while U.S. stocks slid more than 1 percent on concerns about the economy in early 2012.
The European single currency hit a fresh 11-month low against the dollar of $1.291 and a 10-year low against the yen as data showed banks were hoarding the cash recently injected by the European Central Bank rather than lending it out - a bad omen for the European economy in 2012.
If European banks are still this concerned, it's not a good sign, said Karl Schamotta, senior markets strategist with Western Union Business Solutions. That underlines the possibility that this liquidity crunch is getting worse and will continue into the new year.
A strong sale of short-term bonds by Italy Wednesday morning initially brought some relief to European markets, but concerns about Thursday's more challenging auction eventually contributed to the weakness of the euro.
U.S. stock indexes fell more than 1 percent in thin trading as investors feared what many expect to be a tough start to the year. The broad S&P 500 index erased its 2011 gains after just turning positive in last week's rally.
It seems like the weakness in euro, breaking that $1.30 level, really made investors push that 'sell' button, said Ryan Detrick, senior technical strategist with Schaeffer's Investment Research in Cincinnati, Ohio.
But it's somewhat of an exaggerated move, considering that there isn't much volume, and this could end in a one-day selloff.
The Dow Jones industrial average <.DJI> closed down 139.94 points, or 1.14 percent, at 12,151.41, while the Standard & Poor's 500 Index <.SPX> lost 15.79 points, or 1.25 percent, to 1,249.64. The Nasdaq Composite Index <.IXIC> fell 35.22 points, or 1.34 percent, to 2,589.98.
Wall Street's decline weighed on European stocks, which erased early gains. The FTSEurofirst 300 <.FTEU3> index of top European shares fell 0.71 percent to end at 983.32, after rising as much as 0.63 percent earlier in the session.
The MSCI All-Country World index <.MIWD00000PUS> lost 1.34 percent, taking losses for the year to more than 10 percent.
The decline in stocks lifted prices of U.S. government bonds. Benchmark 10-year Treasuries rose 22/32 in price, with the yield at 1.925 percent - below the psychologically significant 2 percent level.
The euro slid to a session low of $1.291, its lowest since January, as investors worried about Italy's sale of 8.5 billion euros worth of debt with maturities of up to 10 years on Thursday. It last traded 1.0 percent weaker at $1.2937.
Against the yen, the euro hit its lowest level since June 2001 at 100.70.
Earlier, the single currency briefly rose against the dollar after Italy's short-term debt costs halved at an auction, helped by a new government austerity package and cheap liquidity from the European Central Bank.
However, Italy will need greater commitment from international investors to sell its bonds on Thursday.
Tomorrow's auction is more important and will give more insight into general sentiment. Today was a warm-up, said Neil Mellor, currency strategist at Bank of New York Mellon.
U.S. crude oil prices fell $1.98 to settle at $99.36 a barrel. They had gained more than one dollar in the previous session following Iran's threat to stop oil shipments through the Strait of Hormuz if Western countries impose new sanctions on its exports.
Tehran faces the prospect of further sanctions from the European Union by the end of January over its nuclear ambitions. Washington said it saw an element of bluster in the threat to close the Gulf, and the U.S. Fifth Fleet said it would not allow any disruption in the world's most important oil route.
The threat by Iran to close the Strait of Hormuz supported the oil market yesterday, but the effect is fading today as it will probably be empty threats as they cannot stop the flow for a longer period due to the amount of U.S. hardware in the area, said Thorbjoern bak Jensen, oil analyst with Global Risk Management.
(Additional reporting by Angela Moon, Edward Krudy and Luciana Lopez; Editing by Kenneth Barry,; Jan Paschal and Dan Grebler)