The international Red Cross said Tuesday that it fears U.S. officials are holding terror suspects secretly in locations across the world.

The Geneva Conventions (search) on the conduct of warfare require the United States to give the Red Cross access to prisoners of war and other detainees.

"We have access to people detained by the United States in Guantanamo Bay (search), Afghanistan and Iraq, but in our understanding there are people that are detained outside these places for which we haven't received notification or access," said Antonella Notari, a spokeswoman for the International Committee of the Red Cross (search).

The United States says it is cooperating with the organization and has allowed Red Cross delegates access to thousands of prisoners, including former Iraqi President Saddam Hussein.

But Notari told The Associated Press that some suspects reported as arrested by the FBI on its Web site, or identified in media reports, are unaccounted for.

"Some of these people who have been reported to be arrested never showed up in any of the places of detention run by the U.S. where we visit," Notari said.

She said she had read media reports that some people are being held at Diego Garcia (search), a British-held island in the Indian Ocean used as a strategic military base by the United States, but the ICRC has not been notified of any prisoners there.

"We just simply have absolutely no confirmation of this in any formal way," she said.

The U.S. government has not officially responded to a Red Cross demand for notification of all detainees, including those held in undisclosed locations, she said.

That request was made by ICRC President Jakob Kellenberger in January during a visit to Washington that featured meetings with Secretary of State Colin Powell, Deputy Defense Secretary Paul Wolfowitz and National Security Adviser Condoleezza Rice.

"So far we haven't had a satisfactory reply," Notari said.

An Army report on the abuses at Baghdad's Abu Ghraib prison found that military police there "routinely held persons brought to them by Other Government Agencies without accounting for them, knowing their identities, or even the reason for their detention."

On at least one occasion they moved these "ghost detainees" around the prison to hide them from a visiting Red Cross delegation, the report by Maj. Gen. Antonio Taguba (search) said. He described the actions as "deceptive, contrary to Army Doctrine, and in violation of international law."

In an interview in Tuesday's edition of the German business daily Handelsblatt, Kellenberger defended the Red Cross policy of refusing to comment publicly on the conditions that it finds in places of detention, preferring to negotiate directly with the authorities.

The international Red Cross came under criticism for not speaking out about the abuse at Abu Ghraib until it was revealed in the media.

"Certain people had the impression that our repeated, confidential approaches to the U.S. authorities were falling flat," Kellenberger said.

"But impressions can be wrong. When we visited Abu Ghraib in January 2004, we found improvements compared with October 2003, and when we visited in March it was better than in January."

The ICRC has, however, spoken out on its concerns over the continued detention without trial of prisoners at Guantanamo Naval Base in Cuba.

"I made it clear in January that we were not happy with the improvements," Kellenberger said.

"The most recent visit has just finished. We must now study the findings."