* FTSEurofirst 300 down 0.2 pct, Euro STOXX 50 down 0.1 pct
* Deutsche Bank down 3.1 pct, warns tapering fears curb revenues
* Commerzbank falls on asset disposal doubts
Financial stocks dragged European shares lower on Wednesday, led by German lenders Deutsche Bank and Commerzbank on concerns about their progress in fixing their balance sheets if liquidity conditions tighten.
Shares in Deutsche Bank fell 3.1 percent as it warned that investment banking revenue would be significantly lower in the third quarter because expectations the U.S. Federal Reserve would begin to unwind its stimulus programme sapped activity in the fixed income market.
"Most of the deleveraging is coming out of the fixed income business," Piers Brown, an analyst at Macquarie Securities, said. "People feel that there's a bit more pressure on Deutsche going forward from the deleveraging plan."
At 1505 GMT, volume on Deutsche shares was already 40 percent higher than its average for the past three months.
Smaller competitor Commerzbank, which is trying to reduce its 347 billion euros ($468.19 billion) book of non-core assets, fell 6.3 percent in volume twice the average after telling analysts no major divestment was on the cards until year-end.
They were among top faller on the FTSEurofirst 300 index of top European shares, which was 0.2 percent lower at 1,255.65 points at 1505 GMT. The euro zone's blue-chip Euro STOXX 50 index was down 0.1 percent, at 2,921.73 points.
The FTSEurofirst 300 has slipped about 1.5 percent since hitting a five-year high last week but it was still on track for a 5.1 percent monthly gain, its best since October 2011.
The market has been fretting about next month's negotiations in Washington to raise the federal debt ceiling to prevent a default, as well as the outlook for the Federal Reserve's stimulus measures after the Fed decided not to scale back the measures last week.
"Investors are still confused about the Fed's monetary policy, and now the focus is switching to negotiations between Democrats and Republicans in Washington. After such a rally, people are now very cautious," said Guillaume Dumans, co-head of research firm 2Bremans.