In addition, the National Institutes of Health plans to spend $18 million over four years to establish three "centers of excellence" to speed research on the currently available cell lines.
"The president's embryonic stem cell policy holds tremendous and yet-untapped potential," Health and Human Services Secretary Tommy Thompson wrote in a letter to be sent to members of Congress on Wednesday. "Before anyone can argue that the stem cell policy should be broadened, we must first exhaust the potential" of currently available lines.
The proposals don't satisfy critics who say Mr. Bush's policy is stifling groundbreaking research, particularly by limiting to just a few the number of cell lines available to study.
"It's window dressing," said Keith Yamamoto, executive vice medical dean at the University of California, San Francisco, a leading center of stem cell research. "The call for more cell lines is not simply that scientists want more of the same. … The fundamental questions we need to ask come partly from what we learn by deriving them."
"This important research field has a cloud over its head," said Rep. Henry Waxman, a California Democrat. "Regrettably, today's announcement doesn't appear to make that future any more certain."
Embryonic stem cells are master cells that form during the early days after conception and can turn into any tissue in the body. Many scientists hope to one day harness them to grow replacement tissue to treat diabetes, spinal cord injuries and other diseases.
But because culling stem cells kills the embryo, which many religious groups oppose, President Bush has ordered the NIH not to fund any research on such cells harvested after Aug. 9, 2001.
Former first lady Nancy Reagan has called for the restrictions to be lifted, and 58 senators from both parties earlier this month asked the president to, also.
In response, HHS' Thompson argues that federal funding of embryonic stem cell research didn't exist before 2001 and now has reached $24.8 million — and says the new proposals should further accelerate it:
Universities including UCSF and Harvard already are doing this so-called translational research using their own money, Yamamoto noted.
Presumptive Democratic nominee Sen. John Kerry of Massachusetts is and open up the field if he is elected.
"We must lift those barriers that stand in the way of stem cell research in America," Kerry has said.
Nancy Reagan became an advocate for stem cell research after her husband was diagnosed with Alzheimer's, one of the diseases that stem cell therapy might someday treat.
The late president's son, Ron Reagan, will call for more stem cell research during a at the Democratic National Convention.