The British scientist who cloned a sheep emphatically restated his opposition to any attempt to clone human beings Wednesday and called for a global drive to ban misuse of the breakthrough technology.

Appearing before a Senate panel taking up the daunting bio-ethical questions brought to the fore by his research, Ian Wilmut said he had not heard of any possible scenario, including trying to save or recreate a dying child, that would make replicating a human being morally acceptable.

I personally could not see any reason we would want to copy a person, he told the Senate subcommittee on public health and safety. We would welcome any efforts that could be made on an international basis (to ban human cloning), he added, urging the United States and Britain to take the lead.

Although public sentiment appears to be firmly against human cloning, Sen. Tom Harkin, an Iowa Democrat, gave a dissenting view. To attempt to limit human knowledge is demeaning to human nature, he said. What utter, utter nonsense to think we can hold up a hand and stay stop it.

Harkin said he expected to see human cloning in his lifetime. I don't fear it at all. I welcome it.

I hope you are wrong, Wilmut told the senator.

Several countries already forbid such research and President Clinton recently imposed a ban on U.S.-funded cloning pending a review by his national bioethics advisers. He also asked the private sector for a voluntary moratorium.

Wilmut was the star witnesses as U.S. lawmakers began grappling with the boundaries of any potential legislation.

Subcommittee chairman Sen. Bill Frist, a Tennessee Republican who was a heart transplant surgeon before entering politics, said he opposed human cloning but wanted society to explore all of the medical, social and ethical implications.

Some lawmakers have clamored for an outright ban on all human cloning research. Sen. Christopher Bond, a Missouri Republican, already has introduced such a bill.

But other lawmakers, scientists and ethicists have called for more cautious wording that would ban cloning people without blocking related research at the cellular level that could revolutionize scientists' understanding of genetics and possibly lead to therapies for diseases including cancer.

Dr. Harold Varmus, National Institutes of Health director, told the Senate panel science and legislation do not mix well, but if Congress does choose to regulate this field it should be extremely cautious not to be too sweeping.

For instance, he said, lawmakers should understand the difference between cloning a human being and working with a blastocyst, a ball of 250 cells at the earliest stage of embryonic development. If there were to be legislation -- I hope it will not be necessary -- be very specific, he said.

Frist said the public must understand and absorb the new findings before it can come to terms with them. He recalled that heart transplants were considered unethical, not scientific, impossible, tyrannical, playing God 30 years ago but now are welcomed and have prolonged thousands of lives.