Libyan leader Muammar Gaddafi was prepared to leave highly enriched uranium potentially unprotected and at risk of hijack in a fit of pique aimed at the UN, US cables revealed by WikiLeaks show.
British newspaper The Guardian said the leaked secret diplomatic cables showed that seven metal casks sealed only for transport, not for storage, were left at a Libyan nuclear facility with a single armed guard in November 2009.
Scientists warned that the 5.2 kilogrammes (11.4 pounds) of uranium in the casks was highly radioactive and rapidly heating up, making it liable to crack the containers and leak into the atmosphere.
The New York Times, which also published the cables, said the US embassy in Tripoli reported: "If the enriched uranium is not removed from the casks within three months, its rising temperature could cause the casks to crack and to release radioactive nuclear material."
US and Russian diplomats frantically lobbied Libyan officials to allow a Russian plane, which had been due to arrive at the Tajoura facility to pick up the casks, to land, but clearance was refused.
The incident came after Gaddafi suddenly reneged on a promise to dispose of the weapons-grade uranium, apparently initially because of a perceived slight when he was barred from pitching a tent outside UN headquarters in New York.
The material had originally formed part of Libya's nuclear weapons plans, which it agreed to abandon in 2003 under pressure from the West.
Anxious US and Russian officials urged the Libyans to ensure the research centre's loading crane was put out of operation to prevent any intruders from moving the casks, each weighing five tonnes, the New York Times reported.
Kadhafi's son Seif al-Islam Kadhafi told the US ambassador that Libya had refused to keep its promise to ship its final enriched uranium stockpile because it was "fed up" with the slow pace of relations with Washington, the cables say.
US and Russian officials eventually managed to placate Moamer Kadhafi and a giant Russian Antonov transport plane was allowed to land at the facility.
On December 21, it took off with the uranium on board.