The United States Wednesday promised a timely and forthright reply to a European Union query over alleged CIA secret prisons and transit flights in Europe of terrorism suspects. The issue is expected to figure in a European trip by Secretary of State Condoleezza Rice next week.

The European query came in a letter to Secretary Rice from British Foreign Secretary Jack Straw, acting in Britain's capacity as the EU's rotating president.

Though the document was not released publicly, officials here said the letter was two paragraphs long and requested clarification on the secret prison reports, which have caused a political uproar in Europe.

At a news briefing, State Department Spokesman Sean McCormack maintained the administration's posture of refusing either to confirm or deny the alleged CIA activity.

But he said the administration will endeavor to respond to the EU letter to the best of its ability, in a timely and forthright manner.

He insisted again that any action regarding terrorist suspects has been in accordance with U.S. law and the American Constitution, and in conformance with U.S. international obligations.

While acknowledging the depth of concern in Europe about the reports, Mr. McCormack also reiterated that the alleged activity should be seen in the context of the unprecedented threat posed by international terrorism.

"All of these questions, concerning allegations of over-flights and secret detainee sites for those who may have engaged, or intended to engage in terrorist activities, all take place within the context of fighting a war against terrorism," he said.  "As I said yesterday, this is a different kind of war. This is a war in which countries, European, American and others around the world, employ all their aspects of national power in order to fight a shadowy enemy."

Mr. McCormack said he had seen no evidence that the issue has diminished U.S. anti-terrorism cooperation with Europe.

He said while it came up during a meeting Tuesday between Ms. Rice and German Foreign Minister Frank-Walter Steinmeier it was in no way the major topic of conversation.

The discussion is likely to continue next week when Secretary Rice visits Germany, Romania, Ukraine and Belgium, where she will attend a NATO foreign ministers meeting in Brussels.

Romania is one of the countries cited in U.S. newspaper reports as a possible host of a clandestine prison facility, but authorities in Bucharest have denied it.

Such reports persist, nonetheless. The New York-based group Human Rights Watch, in a report issued Wednesday, charged that the United States is holding at least 26 so-called ghost detainees in secret overseas locations.

The group said some of them are suspected of involvement in major acts of terror, including the September 2001 attacks in New York and Washington.

But it said the Bush administration has severely compromised chances of prosecuting them for crimes, because of the nature of their detention, and because of reports they may have faced torture or other mistreatment.

The Bush administration denies that any U.S. detainees have been tortured.