Massachusetts Gov. W. Mitt Romney said this week that he will try to ban a method of obtaining stem cells that both Harvard University’s nascent Stem Cell Institute and other researchers in the state currently plan to undertake.

Romney had previously diverged from many other Republicans by offering at least provisional support for stem cell research. But he said this week that he would propose legislation to prevent the creation of embryonic stem cells exclusively for research purposes, citing an “ethical boundary” between using embryos discarded from fertility clinics and creating wholly new ones for scientific experiments.

These restrictions would affect Harvard directly, preventing researchers from carrying out proposed projects, particularly within the Stem Cell Institute. Researchers at the institute have said that the creation of stem cells is critical in allowing scientists to search for cures to hereditary diseases.

University President Lawrence H. Summers reaffirmed his support to Harvard’s scientists yesterday, saying that the ethical questions raised by Romney were not sufficient to merit new restrictions.

“Stem cell research holds important potential to transform the understanding of human diseases and to illuminate possible treatments and cures,” Summers said. “We take seriously the ethical issues involved, which have been subject to careful review at Harvard and at other institutions, and believe that it is vitally important to carefully proceed with such research.”

Romney’s statement followed the introduction of a bill on Wednesday by Massachusetts Senate President Robert E. Travaglini that would facilitate and further protect stem cell research.

Travaglini and other state senators, including Democrat Cynthia S. Creem, have proposed this legislation several times before. Last year, it passed the Senate but was blocked in the House.

And this year, Travaglini made the bill more prominent by promoting it in his inaugural address last month.

But Romney responded yesterday with a critical letter to Travaglini.

“Lofty goals do not justify the creation of life for experimentation or destruction,” he wrote, adding that creation of embryos crosses the boundary of “respect for human life.”

Proponents of Travaglini’s bill have said publicly that they hope to encourage further research at Harvard and other scientific institutions in Massachusetts, which currently face competition from the west coast. California voters approved a referendum last November to offer $3 billion to support stem cell research.

The Massachusetts bill, according to Creem’s legal counsel Sean J. Kealy, was also meant to streamline the legal paperwork currently involved in doing stem cell research, which Kealy said can be time-consuming and very costly.

Kealy added that although no financial incentives are included in the bill, legislators have already started discussing the possibility of offering financial support to attract researchers.

If not, Kealy said, he fears that researchers will “pack their bags and leave.”

“The state law quite stupidly restricts scientific inquiry, and that has to be changed,” he added.