An American research team has succeeded in cloning the first monkey embryos from which stem cells could be removed by adopting the cloning method pioneered by South Korean scholar Hwang Woo-suk.

University of Pittsburgh researchers, led by senior researcher Gerald Schatten, presented their findings at the annual American Society for Cell Biology meeting in Washington on Tuesday.

While the researchers did not achieve a live clone birth, they could grow macaque monkey embryos to about 200 cells, the stage at which the embryo is called a blastocyst and stem cells could be removed. The research team says it's the most developed monkey embryo anyone has grown to date. In previous efforts, the clones died at the 16-cell stage.

The latest study by the Pittsburgh research team applied Seoul National University Professor Hwang's cloning method, which involves removing the nucleus of the egg, then replacing the nucleus with a cell from the person or animal to be cloned.

The Pittsburgh study shows that Hwang's method can also be effective in cloning primates, a feat that researchers had, until now, believed might be impossible.