North Korean doctors, who treated former leader Kim Jong-Il after his stroke in 2008 were sent to the United States for training, said a South Korean doctor on Thursday.
Pyongyang's ambassador to the United Nations had asked the MD Anderson Cancer Center -- based in Houston and part of the University of Texas -- to train three North Korean doctors, Lee Byung-Hoon told AFP.
"The chief of the centre contacted the US government after being asked to secretly meet the North's ambassador, and got approval to accept them as exchange scholars," said Lee, an adviser to the Korean Medical Association.
The communist North habitually lambasts the United States as "warmongers" and the "imperialist enemy."
One of the three specialised in diabetes, another in heart diseases and a third in strokes, Lee said. They trained for three months and the centre later accepted nine more doctors from the communist state.
"They are known to have been a part of Kim's personal medical team and US doctors who trained them came to be aware of details of Kim's medical condition," said Lee, adding their visits were funded by the US government.
The North also asked the US centre to send latest research papers on heart diseases a month before Kim died of a heart attack on December 17, Lee said.
"Apparently they knew Kim's heart condition was getting serious," he said, adding the US doctors did send the material.
Kim, who ruled the impoverished but nuclear-armed country for 17 years, suffered a stroke in August 2008 and is also thought to have had diabetes.