In an unusually strongly worded statement from the ICRC, President Jakob Kellenberger "deplored" the fact that Secretary of State Condoleezza Rice, Defense Secretary Donald Rumsfeld and other U.S. officials had not granted access to hidden prisons.
"No matter how legitimate the grounds for detention, there exists no right to conceal a person's whereabouts or to deny that he or she is being detained, " Kellenberger said in a statement following a series of meetings in Washington.
The ICRC is designated by the Geneva Conventions on warfare as the organization to visit prisoners of war. It is the only international body the United States lets visit terrorist suspects held in Iraq, Afghanistan, Guantanamo Bay, Cuba, but has been demanding access to prisoners held in "undisclosed locations" for more than two years, reported the Associated Press.
U.S. officials contacted at the American mission to international organizations in Geneva said they had no immediate comment, according to the AP.
State Department spokesman Adam Ereli said earlier that the U.S. government provides access to the vast majority of detainees even though it doesn't regard al-Qaida members as covered by the Geneva Conventions.
Kellenberger said in the statement that the ICRC would continue to seek access "as a matter of priority" despite the "disappointing lack of results and the current U.S. position."
The criticism came days after Britain's Attorney General Lord Goldsmith condemned the existence of Guantanamo Bay as "unacceptable."
"Not only would it in my personal opinion be right to close Guantanamo as a matter of principle, I believe it would also help to remove what has become a symbol to many -- right or wrong -- of injustice," he said in a speech.
The criticism of Guantanamo Bay, where about 500 terrorism suspects have been held without charge for as long as four years, was the strongest from an official from the long-standing U.S. ally, Britain.
Goldsmith, who met with U.S. officials to discuss the fate of nine British citizens detained at the prison, said Britain had not been able to accept U.S. proposals for military tribunals for the detainees, according to the AP.
The U.S. Supreme Court is expected to decide in June whether the tribunals are legal.