Representative Bartlett said the Lanza method "has come at a very propitious time" because the Senate is considering various stem cell bills, including a counterpart to legislation he proposed in the House advocating research into alternative ways of deriving embryonic stem cells.

It is not yet clear if human embryonic stem cells generated from blastomeres would be eligible for federal financial support, because they might still fall foul of the Dickey-Wicker amendment, which prohibits federal research where human embryos are destroyed, discarded or subjected to substantial risk.

Dr. Lanza's company, Advanced Cell Technology, is well known in the cloning field, having accomplished solid achievements as well as some that veered toward the merely attention getting, like letting a human nucleus develop to very early stages in a cow's egg. The company is headed by Michael West, who as founder of Geron initiated support for the research that led to the first derivation of human embryonic cells.

It will take a lot more research and maybe several years before Advanced Cell Technology and others can tell if the new method works in humans and how applicable it may be.

In preimplantation genetic diagnosis, there is very little time before the disease-free embryo must be implanted in the uterus, perhaps too little to allow an embryonic stem cell line to be generated, as Dr. Lanza hopes, some experts said.

The procedure is in any case highly inefficient at present, and may never become practical for babies born through in vitro fertilization. "I think it is wildly speculative to say that in the future every IVF child will have embryonic stem cell lines made, especially if the efficiency is so low already," said Dr. Hogan, of Duke.