While many Americans came to believe in the wake of the September 11 attacks that terrorists were at their doorstep, ready to strike anytime, Europeans have a different perception, they say.

"On the US side there is a sense of imminent threat, that we cannot waste time by going through courts, finding evidence," Simon Serfaty, an expert on European affairs at the Centre for Strategic and International Studies in Washington, told AFP.

"On the European side there is a sense that the threat is not so very imminent so that you can take your time thinking through the issue and not make compromises between ends and means."

Dieter Dettke, an expert on German politics at the Washington office of the Friedrich Ebert Foundation, said the uproar in Europe over the prison camps reflected the differing approaches to terrorism.

"We do have a more legalistic perspective on the war on terror and America is far less concerned about legalities," he said.

Allegations that the CIA set up secret prisons, or "black sites", in several eastern European countries to interrogate terrorist suspects and that it had used airports across the continent to transport these suspects in the wake of the September 11 attacks first surfaced last month.

The existence of the prisons would be in violation of the European Convention of Human Rights and the European Union's justice commissioner has warned that any EU country found to have hosted a secret CIA jail would have its voting rights suspended.

Washington initially refused to address the issue, but faced with mounting fury in Europe and a formal EU request for an explanation it has vowed to provide a forthright response.