Nato has denied that one of its Kosovo detention centres has been used by the US to interrogate militant Islamist suspects under its rendition programme.
Nato official James Appathurai told the BBC the alliance had nothing to hide.
He said all former detainees had been held for their activities in Kosovo, adding that there were no longer detainees at Camp Bondsteel.
European democracy watchdog the Council of Europe has urged Nato to allow investigators into the camp.
"If there is nothing to hide, the Council of Europe Committee for the Prevention of Torture should be given immediate and unlimited access," said Council of Europe chairman Terry Davis.
The Council of Europe, which has unlimited access to all prisons run by the UN in Kosovo, has been trying to reach agreement with Nato for more than a year to enable anti-torture investigators to inspect the camp.
"If there are skeletons in the K-For cupboard, the eve of the talks on the future status of Kosovo provides a last-minute opportunity to get them out," Mr Davis said.
Talks on the final status of Kosovo are due to begin later this month.