Researchers at Harvard University said on Tuesday they have started efforts to clone human embryos as a source of valued stem cells, using only private money to bypass federal restrictions on such work.

Ampoules containing a medium for stem cell storage are displayed in London in a 2004 file photo. Researchers at Harvard University said on Tuesday they have started efforts to clone human embryos as a source of valued stem cells, using only private money to bypass federal restrictions on such work. [Reuters]

The scientists are studying how embryonic stem cells are programmed, will try to correct defects and then try to return the repaired cells to the body to battle diseases like blood disorders, ALS, known as Lou Gehrig's disease, and diabetes.

"Our long-term goal is to create embryonic stem cells from a patient's tissues, correct the genetic defects, and get the repaired cells back into the patients," researcher Dr. George Daley of Children's Hospital in Boston said.

The research is controversial because scientists use human embryos which some people say amounts to taking a human life.

The issue has divided Congress, with some lawmakers wanting to give it more funding and others wanting to ban it altogether. President George W. Bush in 2001 restricted the use of federal money for human embryonic stem cell work to a few existing batches of cells.

But Harvard Provost Stephen Hyman told reporters that the project, which he said is critically important to trying to fight often deadly diseases, has been carefully reviewed and that the team of scientists will follow strict guidelines.

Stem cells are the body's master cells and embryonic stem cells are especially powerful because they can produce any kind of tissue in the body and can be grown, virtually immortal, in laboratory dishes.

The Harvard project, which Daley said will cost millions of dollars, will be financed exclusively by private donors with not one penny of public money.

While Harvard is not alone in trying to clone human stem cells, its effort become America's hub for life sciences is well known. Next year it will break ground on 500,000-square-foot (46,500-square-meter) science complex that will house the Harvard Stem Cell Institute.

The field has been marred by scandals.

Several months ago a South Korean researcher who claimed to have cloned human embryos and obtained stem cells from them was found to have falsified his reports. Other groups claimed to have cloned actual human babies but have never produced evidence to support their claims.

Acknowledging that "we will be held to exceedingly high standards to get our work published," Daley said independent auditors will ultimately be able to verify the Harvard work.

The Harvard scientists made an exception in talking about their work before it is published because of keen public interest but said they will not discuss more details until they are ready to submit the work for publication.

The Boston researchers eventually want to use cloning technology to make days-old embryos that could then be used as a source of stem cells.

This process is called nuclear transfer and involves taking the nucleus from a cell, such as a skin cell, inserting it into a human egg cell and reprogramming the egg cell so it starts growing as a human embryo.

Another way to clone embryos is to use the nucleus from a cell taken from a week-old embryo and Daley said they will start here, using leftover embryos from a Harvard fertility clinic and from women who want to donate eggs.