Scientists who routinely clone animal embryos said that cloning human embryos should be just as easy. "I see no reason on earth why it could not be done," said Dr. Robert McKinnell, a professor of genetics and cell biology at the University of Minnesota.

Dr. McKinnell explained that it was much harder to take a cell from an adult organism and use it to make embryos or even clones, since the cells of adult organisms are committed to specific functions and have switched off their capacity for full development. Biologists do not yet understand how to reverse these switches. In the laboratory, a new organism can be cloned from a single cell of a mature plant, but not from an adult mammal.

"If you live to be 100, a liver is a liver and it doesn't turn into brain and it doesn't turn into muscle," Dr. McKinnell said. But ethicists said the very fact that this type of cloning in the new experiment is easy made the question of human clones so intriguing. 'It's Fairly Simple'

"It's not scientifically rich, but that's what makes it morally and legally of concern," said Dr. Arthur Caplan, director of the Center for Bioethics at the University of Minnesota. "It doesn't take a Nobel Prize team with a million-dollar lab. It's fairly simple." Despite the scruples of most scientists, he said, there is no way to control or contain the technology.

The ethical implications are perplexing, experts said. Any time scientists seem to be meddling with the stuff of human life, thorny questions about propriety arise.

George Annas, an ethicist and a health lawyer at Boston University, said that about 10 years ago, researchers considered the possibility of cloning human embryos some day, but rejected it out of hand. "This is the experiment we were never going to do," he said. "It's a horror story. There is nothing to prevent anyone from doing any of this stuff. We're at a stage of genetics that what can be done will be done."

Several infertility experts, who run in vitro fertilization programs, said they have no intention of cloning human embryos even if it is feasible. 'Not a Good Thing'