"The markets are readying themselves for concrete news now but the slow progress of politics could mean the markets are setting themselves up for a fall," said Jane Foley of Rabobank.
Meanwhile, whatever happens with the EU, the larger global economy still looks fairly weak, and oil fell again Wednesday on expectations that slow growth would weaken demand for raw materials.
Benchmark oil in New York fell 68 cents to $83.77 a barrel.
Earlier, shares in Asia lost steam after spending the morning in positive territory.Japan's Nikkei 225 index eked out a gain of less than 0.1% to close up just 5.70 points at 8,615.65. Australia's S&P/ASX 200 was 0.9% higher at 4,039.50. But South Korea's Kospi gave up earlier gains and closed down 0.7% to 1,723.09. Hong Kong's Hang Seng sank 0.7% to 18,011.06 while benchmarks in Singapore and Thailand also fell.