Ronald Green, an ethicist at Dartmouth College, said it would be “very hard for people to say that what is created here is a nascent form of human life that should be protected.” The new technique, if adaptable to human cells, “will be one way this debate could end,” Mr. Green said.

Biologists learned how to generate human embryonic stem cells in 1998 from the few-day-old embryos discarded by fertility clinics, a procedure the embryos did not survive. This source proved controversial, and biologists supported by federal financing were unable to explore the new opportunity until August 2001 when President Bush, in a political compromise, decreed that research on human embryonic stem cells could begin, but only with cell lines already in existence by that date.

The restrictions have caused considerable frustration among biologists and other supporters of research on embryonic stem cells. Indeed, the House is expected to vote today to increase federal funds for such research. If approved, the bill, similar to one approved by the Senate, would go to the president. The White House has already said that the president would veto it.

The new technique, when adaptable to human cells, should sidestep all these problems. James Battey, vice chairman of the National Institutes of Health stem cell task force, said he saw “no impediment at all” to federal support of researchers using the new technique on human cells.

Ever since the creation of Dolly, the first cloned mammal, scientists have sought to lay hands on the mysterious chemicals with which an egg will reprogram a mature cell nucleus injected into it and set the cell on the same path of embryonic development as when egg and sperm combine.

Years of patient research have identified many of the genes that are active in the embryonic cell and maintain its pluripotency, or ability to morph into many different tissues. Last year Dr. Yamanaka and his colleague Kazutoshi Takahashi, both at Kyoto University, published a remarkable report relating how they had guessed at 24 genes responsible for maintaining pluripotency in mouse embryonic stem cells.

When they inserted all 24 genes into mouse skin cells, some of the cells showed signs of pluripotency. The Kyoto team then subtracted genes one by one until they had a set of four genes that were essential. The genes are inserted into viruses that infect the cell and become active as the virus replicates. The skin cell’s own copies of these genes are repressed since they would interfere with its function. “We were very surprised” that just four genes are sufficient to reprogram the skin cells, Dr. Yamanaka said.