Hwang Woo-suk, the South Korean scientist who cloned a human embryo last year, announced this week that he had created the first embryonic stem cells that genetically match injured or sick patients.

The match means the stem cells, the building blocks of all bodily tissues, are unlikely to be rejected by the body's immune system. Researchers hope the cells eventually can be used to repair damage from disease.

Still, the South Korean team was cautious about giving a timeframe.

"Some foreign researchers have said three to five decades, some have said in just several years," said Ahn Curie, a doctor of transplantation medicine at Seoul National University Hospital, and a member of Hwang's team. "We will work hard, but we don't want to raise false expectations."

Other scientists have lauded the advances made by Hwang's team -- and their speed. But Hwang, a professor at Seoul National University, said the researchers were working methodically, especially due to ethical concerns.

"We already had the technological know-how last year, at the time of the human embryo cloning," Hwang told reporters late Friday at Incheon International Airport near Seoul. "But our team imposed a moratorium on our own, because there were ethical issues."

President Bush expressed concern about the South Korean research and a spokesman said the South Korean work amounted to human cloning for the sole purpose of research.

A top Vatican official on Saturday condemned the creation of cloned embryos, describing it as a crime.

"It must be underlined that here ... human rights is being violated," Monsignor Elio Sgreccia, who heads the Pontifical Academy for Life, told Vatican Radio.

Last year, Hwang's team cloned stem cells from one healthy woman. This year, they created 11 batches of stem cells that genetically match men or women with either spinal cord injuries, diabetes or a genetic immune disease.