At 0709 GMT, the FTSEurofirst 300 index of top European shares was down 0.7 percent at 1,091.05 points. It rose 0.7 percent on Wednesday after declines in the previous three straight sessions. The index is down 2.1 percent this week.

Moody's said late on Wednesday it saw a rising possibility that the statutory US debt limit will not be raised on a timely basis, leading to a default on US Treasury debt obligations.

"US debt situation is annoying. It's politics pure and simple. I guess they'll get out of it in time so no harm will be done," said Koen De Leus, strategist at KBC Securities.

"But it does create additional nervousness on the top of all other issues like the uncertainty about US growth in the second half of 2011, inflation problems in emerging countries and the European debt problem."

Technology shares featured among the top decliners, with the sector index down 1.9 percent. Software AG fell 13 percent on disappointing quarterly sales figures.

Copyright Reuters, 2011