The idea of doing this in people is controversial because the embryos have to be destroyed to obtain the stem cells.
Despite the monkey success, "we're still far off to start dreaming about translating this technique to humans," Cibelli said. That's because the reported results were very inefficient, requiring many eggs to produce stem cells, he said.
Still, the work shows monkeys can be used to study the potential of embryonic stem cells produced through cloning, Cibelli said. "That's a terrific tool."
Cloning is most famous for producing not stem cells but baby animals, such as Dolly the sheep. But while some people may view the new development as a move by scientists on the "slippery slope" toward producing cloned human babies, "we're all opposed to that," Cibelli said.
Jim Newman, a spokesman for the Oregon Health & Science University, which operates the primate center where Mitalipov works, declined to confirm whether the scientist had cloned monkey embryos. But he said a study in that area of research will be released soon by the scientific journal Nature.
Katie McGoldrick, a Nature spokeswoman in Washington, said she could not discuss papers that may or may not have been submitted for publication.
The primate center was in the news for another reason Tuesday. An activist group, People for the Ethical Treatment of Animals, said it had documented violations of animal protection laws there. University officials said the primate center has an excellent record for animal care.