A report by the International Committee of the Red Cross, quoted Tuesday by the New York Times, accuses the U.S. military of using interrogation tactics that amount to torture against prisoners at the Guantanamo Bay detention center in Cuba. Bush administration spokesmen said the detainees are being treated humanely and that the United States does not condone torture.

Neither the Red Cross in Geneva nor the U.S. government has publicly released the text of what the New York Times said was a confidential report on the treatment of Guantanamo detainees.

But they are also not contesting the newspaper account, which says the Red Cross document alleges that the U.S. military has intentionally used psychological and sometimes physical coercion on prisoners that is, in its words, "tantamount to torture."

The International Red Cross is the only independent monitor allowed to visit the U.S. naval facility in Cuba, which houses about 550 prisoners, most of them alleged enemy combatants detained in Afghanistan after the U.S.-led invasion in 2001.

The critical finding on the handling of prisoners came after a visit by a Red Cross inspection team that spent most of last June at Guantanamo.

The report, as quoted by the New York Times, said the team found a system designed to break the will of prisoners, through such tactics as humiliation, solitary confinement and exposure to loud music and extreme temperatures.

Red Cross inspectors had reported abuses in previous visits. But those alleged in the new report are said to have been more refined and repressive than what was observed in the past.

The report was said to have been delivered to the commander of the Guantanamo facility and lawyers at the State Department, the Pentagon and White House in July. The publication of its contents Tuesday drew sharp denials from administration officials that the United States is mistreating prisoners.

White House Press Secretary Scott McClellan insisted the Guantanamo detainees are "being treated humanely" even though they were combatants picked up on the battlefield who were seeking to harm the United States.

At a briefing in Washington, State Department Spokesman Richard Boucher said the United States does not condone the torture of prisoners and treats those at Guantanamo in conformance with international standards:

"We have said before that we think the detainees kept there are kept, are held, in humane conditions that take into account the various security and other problems these prisoners might present," said Mr. Boucher.  "But they are treated humanely and in accordance with standard international, with relevant international, practice."

U.S. human rights activists said they were not surprised by the allegations, following another leaked International Red Cross report last May describing mistreatment of U.S.-held prisoners in Iraq.

The vice president of the New York-based Center for Constitutional Rights, Peter Weiss, whose group filed a criminal complaint in Germany Tuesday over alleged U.S. prisoner mistreatment in Iraq, said the new report fits a pattern of abuse by the Bush administration:

"The United States administration has gone out of its way to destroy the whole fabric of the laws of war," said Mr. Weiss.  "They have redefined torture, they have redefined the laws of war, and they have given themselves the right to disregard the Geneva conventions."

A spokeswoman for the Red Cross in Geneva acknowledged that the report had gone to the U.S. government, but said the organization would not break its vow of confidentiality as to its findings, saying that is the best way to improve conditions for detainees.

She did acknowledge what she termed "significant problems" regarding the conditions and treatment of Guantanamo detainees that have still not been addressed by the U.S. government.

State Department Spokesman Boucher said the United States has an active ongoing dialogue with the International Red Cross about issues involving the prisoners, and takes its reports on the subject "very, very seriously."

He said the Pentagon talks to the Red Cross "all the time" about issues relating to Guantanamo, and has set up a special bureau, the Office of Detainee Affairs, to deal with the organization on issues concerning the "welfare and situation" of the prisoners.