Harvard researchers said Wednesday they had asked the university’s ethics boards for permission to create cloned human embryos for medical research, marking the first push to conduct such experiments at a U.S. academic institution.

The goal of the ethically contentious, privately financed work, which has already gained provisional approval from one Harvard committee, is to develop new cures for diabetes, Parkinson’s disease and other ailments. The approach involves creating cloned human embryos that would be destroyed within days to retrieve stem cells growing within.

Several lines of evidence suggest stem cells from cloned embryos have greater potential as medical treatments than stem cells derived from unused embryos at fertility clinics, which are created by in vitro fertilization and are now the major source of stem cells for research.

Opponents, however, say it is wrong to create human embryos solely for the purpose of destroying them. Some also fear the work could speed the arrival of the first cloned baby, an outcome that virtually all parties to the debate expressly oppose.

The Harvard move comes at a politically precarious time, as stem-cell research has emerged as a potent wedge issue among voters in the razor-close presidential election.

President Bush has encouraged Congress to pass legislation banning all human embryo cloning, and the House has repeatedly voted to do so. The Senate has remained split on the issue.

Democratic challenger Sen. John Kerry has said he supports research on cloned embryos with proper federal and institutional oversight.

The United Nations, too, is embroiled in the issue. On Oct. 21 it will renew a twice-stymied effort to gain international consensus on whether to ban the creation of cloned embryos and cloned babies, or only babies. Some countries have already said they would not abide by a broader ban.

The Harvard application highlights an evolving migration of U.S. human embryonic stem-cell research from the federal research arena into the far less regulated private sector as scientists grow frustrated by restrictions on government funding.

An executive order signed by Bush in 2001 allowed only limited use of federal funds for human embryonic stem cell research and banned federal support for research involving human embryo clones.

The Harvard proposal, submitted by stem cell researcher Douglas Melton, calls for the creation of human embryos that would be genetic replicas of various patients with type 1 diabetes, Parkinson’s disease and Alzheimer’s disease, said Charles Jennings, executive director of the Harvard Stem Cell Institute, where Melton’s work would be done. The institute was formed earlier this year.

Stem cells retrieved from those embryos would carry the exact collection of genetic glitches — many of them as yet unidentified by scientists — that cause those diseases. By watching what goes wrong with those cells as they mature in laboratory dishes — into brain cells, for example, in the case of Parkinson’s — scientists hope to discover underlying causes of the diseases and test drugs to see if they can correct the problems.