Donald Rickard said he and his handlers believed Mandela was "the world's most dangerous communist outside of the Soviet Union" and he had no qualms about tipping the authorities off about his whereabouts in 1962, the height of the Cold War.
Mandela's detention at a police roadblock in Howick, KwaZulu Natal was the catalyst for a series of trials, culminating in the Rivonia Treason Trial that would see him spend 27 years in prison. The CIA's involvement in his detention after 17 years on the run has long been suspected but has never been confirmed until now.
Rickard, the then US vice-consul in Durban, suggested that ANC informants told him Mandela was visiting the seaside city and said he told South African police when he learned the activist was due to return to Johannesburg.
Mandela, Rickard believed, was "completely under the control of the Soviet Union, a toy of the communists", and was about "to incite" the Indian population of Natal into a communist-led mass rebellion against the apartheid government which could open the door to Russian intervention.
"Natal was a cauldron at the time," Rickard said "and Mandela would have welcomed a war. If the Soviets had come in force, the United States would have had to get involved, and things could have gone to hell".
"We were teetering on the brink here and it had to be stopped, which meant Mandela had to be stopped. And I put a stop to it."
The 88-year-old broke his silence about his involvement in netting the "Black Pimpernel", as Mandela was known, in an interview in March with researchers for a new film by British director John Irvin, entitled Mandela's Gun, which will be screened at the Cannes Film Festival next week.
Rickard, who retired from the CIA in 1978 and spent the rest of his life in a remote spot in Colorado, died two weeks after the interview.
Zizi Kodwa, a spokesman for the ANC, said the revelation was "a serious indictment" but nothing new.
"We always knew there was always collaboration between some Western countries and the apartheid regime," he said.
He echoed claims by the ANC's secretary-general that the ANC was still interfering in South African politics.
"We have recently observed that there are efforts to undermine the democratically elected ANC government," he said. "It is still happening now - the CIA is still collaborating with those who want regime change."
Bantu Holomisa, a close friend of Mandela and now leader of an opposition party, said an apology from the US would not go amiss.
"They can apologise, I am sure it would be welcomed if they were to say it - we would accept it as a symbolic gesture," he said.
George Bizos, Mandela's long-time lawyer who defended him and his associates at the Rivonia Trial, said the West played both honourable and dishonourable roles in the struggle against apartheid.
"We never knew for certain that (the CIA) were involved but it was thought to be a probability because of the ideology of the United States at the time," he told The Telegraph. "I don't think President John F Kennedy's government was particularly pleased with Nelson Mandela."
If the Soviets had come in force, the United States would have had to get involved, and things could have gone to hell
He said Mandela had "unwisely" attended a party held in his honour after his return from overseas shortly before his arrest. "There were thought to have been people there that may have been informants who set up a trap for him," he said.
The lawyer said the Americans were also instrumental in the trade blockade that brought the apartheid government to its knees, and visited Mandela in prison.
He added that the close involvement of the British authorities was also clear, and that the British consul general had told him the night before the Rivonia trial sentencing that Mandela would not be hanged.
Mandela became South Africa's first black president in 1994. He died in December 2013 aged 95.
The US Government has declined to comment on the reports.