The study leader Anthony Atala, director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine in Winston-Salem, N.C., said that the amniotic fluid cells grow as fast as embryonic stem cells.

It took Atala's team some seven years of research to determine the cells they found were truly stem cells that "can be used to produce a broad range of cells that may be valuable for therapy."

However, the scientists noted they still don't know exactly how many different cell types can be made from the stem cells found in amniotic fluid. They also said that even preliminary tests in patients are years away.

Atala and other scientists said they doubt the cells will make embryonic stem cells irrelevant.

"There's not going to be one shoe that fits all," said Robert Lanza, scientific director at Advanced Cell Technology in Worcester, Mass.

Harvard stem cell researcher George Daley said the new cells "are not a replacement for embryonic stem cells."

The House of Representatives is scheduled to vote this week on a bill that would have permitted federal funding of research on some embryonic stem cells.