In practice, though, the CIA has little control over prisoners once they leave CIA custody, said three recently retired CIA officials and other intelligence officials who have dealt with foreign intelligence services on detainee matters.
"These are sovereign countries," said Michael Scheuer, a recently retired CIA officer who favors the use of renditions to disrupt terrorist networks. "They are not going to let you into their prisons."
At a news briefing, President Bush defended the practice of transferring suspected terrorists to countries of origin.
(Bill O'leary -- The Washigton Post)
Today, 12:30 p.m. ET: Post reporter Dana Priest will take your questions on the CIA's rendition policies.
"Once they are in the jurisdiction of another country, we have no rights to follow up," said Edward S. Walker Jr., a former assistant secretary of state for Near Eastern affairs and now president of the Middle East Institute.
The U.S. official who visited foreign detention sites said the issue "goes far beyond" the assurance: "They say they are not abusing them, and that satisfies the legal requirement, but we all know they do."
For a country offering assurances, following up could imply the United States does not trust its leaders.
"We wouldn't accept the premise that we would make a promise and violate it," said the Egyptian ambassador to the United States, Nabil Fahmy, whose country has accepted rendered terrorism suspects. He denied that Egyptian officers employ torture in interrogations. "I don't accept the premise that if you want to torture someone, you send them to Jordan or Egypt. That would be the exception to the rule." Egypt, he added, "is becoming more and more rigorous" in prosecuting officers who use excessive force.
But Mamdouh Habib, an Australian citizen, has alleged he was tortured in Egypt for six months after U.S. officials sent him there. Habib had been detained in Pakistan in October 2001 as a suspected al Qaeda trainer. In Egypt, he alleges, he was hung by his arms from hooks, shocked, nearly drowned and brutally beaten. He was then sent to the U.S. military prison at Guantanamo Bay, Cuba, and was released in February.
Another Arab diplomat, whose country is actively engaged in counterterrorism operations and shares intelligence with the CIA, said it is unrealistic to believe the CIA really wants to follow up on the assurances. "It would be stupid to keep track of them because then you would know what's going on," he said. "It's really more like 'Don't ask, don't tell.' "
Questions about assurances have stalled the release of prisoners from Guantanamo.
Guarantees of humane treatment by Yemen notwithstanding, a federal court in the District of Columbia prohibited on Saturday the transfer of 13 Yemeni prisoners from Guantanamo to Yemen until a hearing is held on their attorneys' assertion that they could be tortured if returned there.
And despite assurances by China, State Department officials have been unwilling to send 22 Chinese Muslims from Guantanamo to China for fear they would be tortured.
Researcher Julie Tate contributed to this report.