south korea's pioneering stem cell scientist has cloned a dog, smashing another biological barrier and reigniting a fierce ethical debate - while producing a perky, lovable puppy.

the researchers, led by hwang woo-suk, insist they cloned an afghan hound, a resplendent supermodel in a world of mutts, only to help investigate human disease, including the possibility of cloning stem cells for treatment purposes.

but others immediately renewed calls for a global ban on human reproductive cloning before the technology moves any farther.

"successful cloning of an increasing number of species confirms the general impression that it would be possible to clone any mammalian species, including humans," said ian wilmut, a reproductive biologist at the university of edinburgh who produced the first cloned mammal, dolly the sheep, from an adult cell nearly a decade ago.

researchers have since cloned cats, goats, cows, mice, pigs, rabbits, horses, deer, mules and gaur, a large wild ox of southeast asia. so far, efforts to clone a monkey or another primate with the same techniques have failed.

uncertainties about the health and life span of cloned animals persist; dolly died prematurely in 2003 after developing cancer and arthritis.

wilmut and others complimented hwang's achievement, reported wednesday in the journal nature. but they said politicians and scientists must face the larger and more delicate issue - how to extend research without crossing the moral boundary of duplicating human life in the lab.

"the ability to use the underlying technology in developing research models and eventually therapies is incredibly promising," said robert schenken, president of the american society for reproductive medicine. "however, the paper also points out that in dogs as in most species, cloning for reproductive purposes is unsafe."

the cloned puppy was the lone success from more than 100 dogs implanted with more than 1,000 cloned embryos.

in a news conference in seoul, the cloning team also condemned the reproductive cloning of humans as "unsafe and inefficient." human reproductive cloning already is banned in south korea. other nations, including the united states, are split over whether to ban just human cloning or cloning of all kinds, including the production of stem cells. 

(agencies)