Scientists have devised two new techniques to derive embryonic stem cells in mice, one of which avoids the destruction of the embryo, a development that could have the potential to shift the grounds of the longstanding political debate about human stem cell research.

The destruction of embryos is a principal objection of anti-abortion advocates who have strenuously opposed federal financing of the research.

The second new technique manipulates embryos so they are inherently incapable of implanting in the uterus, what some see as a possible ethical advantage in the proposed therapy, which converts a patient's skin cell into embryonic cells and then new tissues to repair the body. Both methods are described in today's online edition of Nature.

The technique for making embryonic stem cells without compromising the embryo has yet to be adapted to people, but the two species are very similar at this level of embryonic development. "I can't think of a reason why the technique would not theoretically work in humans," said Brigid L. M. Hogan, an embryologist at Duke University.

If it does work in people, which could take many months to find out, the technique might divide the anti-abortion movement into those who accept or reject in vitro fertilization, because the objection to deriving human embryonic stem cells would come to rest on creating the embryos in the first place, not on their destruction.

"This gets around all of the ethical arguments, except for that small minority of the pro-life community that doesn't even support in vitro fertilization," said Representative Roscoe G. Bartlett, Republican of Maryland, whose Web site describes him as "a pro-life legislator."

Until now the only way of deriving human embryonic stem cells has been to break open the embryo before it implants in the uterus, a stage at which it is called a blastocyst, and take out the inner cell mass, whose cells form all the tissues in a human body.

Although the blastocysts used in the procedure are ones that fertility clinics have rejected for implantation, many opponents of abortion say the destruction of any embryo is wrong. Congress has forbidden the use of federal money for any such research, and federally supported scientists can work with only a small number of existing lines of embryonic stem cells that have been exempted by President Bush.

Robert Lanza and colleagues at Advanced Cell Technology, a biotechnology company in Worcester, Mass., have developed an alternative way of generating embryonic stem cells that leaves the embryo viable.

They let a fertilized mouse egg divide three times until it contained eight cells, a stage just before the embryo becomes a blastocyst. Removing one of these cells, they then coaxed it into growing in glassware and forming cells that have all the same essential properties as embryonic stem cells derived from the inner cell mass, Dr. Lanza's team reports.