Tripoli, Libya ? The CIA and other Western intelligence agencies worked closely with the ousted regime of Moammar Gadhafi, sharing tips and cooperating in handing over terror suspects for interrogation to a regime known to use torture, according to a trove of security documents discovered after the fall of Tripoli.

The revelations provide new details on the West’s efforts to turn Libya’s mercurial leader from foe to ally and provide an embarrassing example of the U.S. administration’s collaboration with authoritarian regimes in the war on terror.

The documents, among tens of thousands found in an External Security building in Tripoli, show an increasingly warm relationship, with CIA agents proposing to set up a permanent Tripoli office, addressing their Libyan counterparts by their first names and giving them advice. In one memo, a British agent even sends Christmas greetings.

The agencies were known to cooperate as the longtime Libyan ruler worked to overcome his pariah status by stopping his quest for weapons of mass destruction and renouncing support for terrorism. But the new details show a more extensive relationship than was previously known, with Western agencies offering lists of questions for specific detainees and apparently the text for a Gadhafi speech.

They also offer a glimpse into the inner workings of the now-defunct CIA program of extraordinary rendition, through which terror suspects were secretly detained, sent to third countries and sometimes underwent the so-called enhanced interrogation tactics like waterboarding.

The documents mention a half dozen names of people targeted for rendition, including Tripoli’s new rebel military commander, Abdel-Hakim Belhaj.

Peter Bouckaert of Human Rights Watch, which helped find the documents, called the ties between Washington and Gadhafi’s regime “A very dark chapter in American intelligence history.”

“It remains a stain on the record of the American intelligence services that they cooperated with these very abusive intelligence services,” he said Saturday.

The findings could cloud relations between the West and Libya’s new leaders, although Belhaj said he holds no grudge. NATO airstrikes have helped the rebels advance throughout the six-month civil war and continue to target regime forces as rebels hunt for Gadhafi.