"The theme today is clearly Portugal, Libya and Japan which have been largely priced in by the markets, unless there is a major development," said Yves Marcais, dealer at Global Equities in Paris. If the Portuguese government were to lose a parliamentary vote on its austerity policies, the fear is that it would then have no option but to appeal for outside help, Marcais said. Francois Duhen, analyst at CM-CIC Securities, said the situation in Portugal is overshadowing the EU summit in Brussels which is supposed to agree a comprehensive set of measures to resolve the eurozone debt crisis. However, in the event the Portuguese government does fall, then EU leaders will find their choices even more limited, Duhen said. Lisbon closed down 0.99 percent before the vote was called. In New York, the blue-chip Dow Jones Industrial Average was up 0.23 percent at around 1700 GMT while the high-tech Nasdaq Composite index was little changed.

"Japan, which warned of dangerous levels of radioactive iodine in Tokyo's tap water, and Libya (are) likely to remain in the Street's crosshairs," said Andrea Kramer of Schaeffer's Investment Research.

In Asian trade earlier Wednesday, Japanese shares closed sharply lower, falling 1.65 percent after jumping more than seven percent over the previous two sessions on hopes the Fukushima emergency could be controlled. Hong Kong slipped 0.14 percent but Shanghai gained 1.01 percent and Sydney up 0.19 percent.