Secretary of State Condoleezza Rice, on a five-day diplomatic tour of Europe, is defending U.S. antiterrorism tactics, insisting that the practices comply with U.S. and international law.
The United States has been accused by human rights groups of practicing "rendition," where suspects are taken for interrogation to countries that allow torture. Rice has denied the allegations.
"The United States does not use the airspace or airport of any country for the purpose of transporting a detainee when we believe he or she will be tortured," she said Monday.
Rice also has met broad European criticism over an alleged network of secret CIA prisons in European nations. Current and former CIA officers say the United States scrambled to make sure all of the prisoners were out of Europe before her arrival.
The CIA declined to comment, but current and former intelligence officers told ABC News that 11 al Qaeda figures were once held at a former Soviet base in Eastern Europe. Four or five prisoners were later moved to a second country.
"I certainly think it's very worrying that there have been serious allegations about these prisons and also rendition," said Mary Robinson, a former United Nations Human Rights chief. A "real worry about an erosion of standards."
"The military, the CIA are not infallible institutions" said John Sifton of Human Rights Watch. "They make mistakes and that's when it's important to have a check and balance, some transparency, so that innocent people don't get sucked into the system."
Human rights groups have identified a military air base in Poland as one of the secret prisons.
"The president of Poland has said that there is no truth in these reports," said Radoslaw Sikorski, the defense minister of Poland.
Human Rights Watch has also reported a CIA prison site in Romania -- possibly a military base visited last year by Secretary of Defense Donald Rumsfeld.
"There is no evidence concerning either prisons or flights … belonging to the CIA in Romania," said Romanian Prime Minister Calin Tariceanu.
Rice will visit the country later today.
Yet critics like Robinson said that the rumors were troubling -- especially considering that the countries where prisoners are supposedly being rendered are known to "do shocking, inhuman things."
"There is an ambivalence about what includes torture in the U.S,." Robinson said. "It is a sad day when the country that uses a lot of rhetoric about freedom is undermining our heritage."