PARIS, Sept 13 (Reuters) - Euro zone stocks fell on Thursday in thin volumes as investors await to see if the U.S. Federal Reserve will unveil further stimulus measures which could add fresh fuel to the market's sharp three-month rally.
The euro zone's blue chip Euro STOXX 50 index unofficially ended 0.8 percent lower at 2,544.73 points, while the FTSEurofirst 300 index of top European shares closed 0.1 percent lower at 1,106.71 points.
The Fed is expected to launch a third round of quantitative easing later on Thursday and could signal that the frail U.S. economy may warrant ultra-low interest rates for at least another three years.
"There might be a bit of disappointment tonight if the Fed doesn't announce a new round of quantitative easing, but a pull-back after such a strong rally sparked by (ECB head Mario)Draghi's 'magic words' would be quite healthy," said Alain Zeitouni, head of multi-asset management, France, at Russell Investments, which has $166 billion under management.
"But the real question about QE3 is not 'if' the Fed will launch it, it's 'when' it will launch it. If it's not today, it'll be in the next few months."
Euro zone banking stocks were among the top losers, trimming recent lofty gains, with Societe Generale down 2.9 percent and Banco Popolare down 2.3 percent.
Aerospace and defence groups EADS and BAE Systems tumbled 10.4 percent and 7 percent respectively, dragged by doubts over the two companies' merger plans.