Former President Jimmy Carter said Tuesday civil liberties have eroded in the United States since Sept. 11, 2001, and that, in turn, has emboldened governments worldwide to abuse human rights under the guise of fighting terrorism.

The Bush administration set a bad precedent by indefinitely detaining 680 foreign nationals captured in Afghanistan at a U.S. naval base in Cuba, Carter said. The Supreme Court agreed this week to review the legality of the detentions.

Carter also said the United States sent a worrisome signal by rounding up hundreds of Arabs and Muslims in this country for breaking immigration law in the wake of the Sept. 11 attacks. Many were held for months with no formal charges.

"This is a violation of the basic character of my country and it's very disturbing to me," Carter said at an Atlanta conference of rights activists.

The Bush administration contends the measures help it fight the war on terrorism, but some critics worry the United States is losing its moral authority to criticize human rights violations.

Carter's remarks came the same day that Foreign Minister Ana Palacio of Spain, a key U.S. ally in the war on terrorism, said the United States made a "major error" by indefinitely detaining people in Cuba. She said a Spanish national is being held for suspected ties to al-Qaida and "this situation cannot continue."

Bush's staunchest international supporter, British Prime Minister Tony Blair, had also appealed to the president a few months ago on behalf of nine Britons held at the U.S. Navy base at Guantanamo Bay, Cuba. He sought their return to stand trial in Britain or, barring that, a guarantee of a fair trial with no possible death sentence.

Bush has said some detainees at Guantanamo may face military tribunals and the possibility of a firing squad, but he ruled out the death penalty for the Britons.

On Sunday, former Vice President Al Gore urged Congress to repeal the Patriot Act, which expanded the federal government's surveillance and detention power, allowing authorities to conduct secret searches and even monitor the books people read.

The Bush administration is asking Congress to further expand the Patriot Act, which Attorney General John Ashcroft says has helped prevent more terrorist attacks.

A prominent activist who joined Carter at the human rights conference, Saad Ibrahim of Egypt, said: "Every dictator in the world is using what the United States has done under the Patriot Act . . . to justify their past violations of human rights and to declare a license to continue to violate human rights."

Ibrahim, a professor at the American University in Cairo, was jailed for seven years after exposing fraud in the Egyptian election process.

Karin Ryan, senior human rights adviser to the Carter Center, said tyrants also point to the detentions in Cuba to justify harsh measures.

"What dictators all over the world are saying is: 'The United States has no moral authority to criticize human rights violations when they have put in cages more than 600 people without any prospect of a fair trial,' " she said.

In Tunisia, Ryan said, lawyers for people charged with terrorism have themselves been charged as terrorists. Authorities in India used anti-terrorism laws to prosecute people who were protesting the clearing of land to make way for a business development. The president of Colombia, Alvaro Uribe, recently referred to human rights organizers as "politickers at the service of terrorism," the Carter Center said, and defended expansive police powers granted to security forces.

Other examples cited by the Carter Center: Eritrea has shut down independent newspapers and jailed journalists after accusing them of having terrorist ties. And authorities in Uzbekistan imprisoned members of the Human Rights Society on weak evidence alleging they recruited Islamic militants.

This afternoon, Carter plans to outline recommendations to improve the human rights climate. He is scheduled to speak along with Hina Jilani of Pakistan, the United Nations special representative on human rights defenders, and other activists.