Their study fulfils one of the basic promises of using cloning technology in stem cell research -- that a piece of skin could be taken from a patient and used to grow the stem cells.

Researchers believe the cells could one day be trained to provide tailored tissue and organ transplants to cure juvenile diabetes, Parkinson's disease and even to repair severed spinal cords. Unlike so-called adult stem cells, embryonic stem cells have the potential from the beginning to form any cell or tissue in the body.

Woo Suk Hwang and colleagues at Seoul National University report their process is much more efficient than they hoped, and yielded 11 stem cell batches, called lines, from six adults and three children with spinal cord injuries, juvenile diabetes and a rare immune disorder.

"This study shows that embryonic stem cells can be derived using nuclear transfer from patients with illness ... regardless of sex or age," Hwang told reporters in a telephone briefing.

"I am amazed at how much they have accomplished in just a year and the amount, the quality and the vigorousness of their evidence," Dr. Gerald Schatten of the University of Pittsburgh, a stem cell expert who reviewed the study, said in a telephone interview.

While the patients whose cells were copied do not stand at this time to benefit, the researchers hope to study the cells to understand their conditions better.

They also say their method may be less controversial than other work with embryonic stem cells because, by their definition, a human embryo was never actually created.

The report, published in the journal Science, is certain to add to the growing US political controversy over the federal funding of embryonic stem cell research.

Opponents say all such work is unethical and should be banned because human life begins at conception and should not be destroyed.

Hwang said his method differs from that first used to derive human embryonic stem cells in 1998 and he proposes using a new term for the cloned embryos -- a "nuclear transfer construct."

"I think this construct is not an embryo," he said. "There is no fertilisation in our process. We use nuclear transfer technology. I can say this result is not an embryo but a nuclear transfer construct." The sheep Dolly, the first adult mammal cloned, was made using nuclear transfer, in which the nucleus is removed from an egg cell, replaced with the nucleus of the animal or person to be cloned, and then fused. The egg begins dividing as if it had been fertilised and sometimes becomes an embryo.

Cattle, pigs, sheep, cats and other animals have been cloned using this method.

Schatten said when scientists first got stem cells from human embryos in 1998, they broke open the little days-old ball of cells called a blastocyst.

In the current study, he said, they simply laid down the blastocyst in a lab dish filled with human "feeder cells."