Gov. Mitt Romney partially vetoed the embryonic stem-cell research bill on May 12 by proposing four amendments that would affirm that life begins at conception, ban cloning, strengthen protections for women donating their eggs for stem-cell research and tighten restrictions on donating embryos for this research.

In a letter addressed to the Massachusetts legislature, which approved the bill earlier this month, Romney wrote that he proposed the changes in order to “proceed without crossing ethical boundaries,” adding that “the power to conduct this research must be bounded by our respect for human life.”

"This bill allows for the cloning of genetically complete human embryos solely for the purpose of experimentation. Human cloning for any purpose -- whether for research (so-called 'therapeutic cloning') or reproduction (so-called 'reproductive cloning') -- is ethically wrong. Once cloning occurs, a human life is set in motion. It is a complete genetic entity with a full complement of human chromosomes," he wrote.

"Since 1974, Massachusetts law has defined 'unborn child' as 'the individual human life in existence and developing from fertilization until birth,'" he continued. "The bill would fundamentally change this definition and declares that human life now begins upon 'implantation of the embryo in the uterus.'"

Romney called the redefinition “misguided” and proposed striking the section that contains the new definition.

Romney stated that while he supports embryonic stem-cell research on what he called “surplus embryos” created through in-vitro fertilization that would be “otherwise discarded,” he does not support cloning for research.

"The creation of embryos by therapeutic cloning, in the rare instances where this procedure has been attempted, has proven exceedingly difficult. In fact, it has never been successfully accomplished in the United States," he said.

Somatic cell nuclear transfer, is the process by which scientists can form the identical twin of a patient and extract stem-cells from the embryo, thus destroying it, in hopes of curing the patient. Scientists take a woman’s egg, remove the nucleus and insert a nucleus from another person. The egg is then stimulated to form an embryo.

Some are concerned that poor women will be exploited to donate eggs needed for the cloning. Romney has proposed that donors be compensated for only “out-of-pocket costs” and be warned of the risks, which include health complications and, in rare cases, death.

Despite the benefits touted by supporters, embryonic stem-cells have not led to any practical cures while therapies using stem-cells obtained from adult cells and umbilical cord blood have been used to successfully treat ailments such as spinal cord injury, diabetes and stroke.

Scientists in Massachusetts who want to perform research on embryonic stem-cells are currently required to obtain approval from the local district attorney. The bill, without Romney’s partial veto, would remove that requirement and give the state Health Department limited regulatory controls. It would prevent research to cloned embryos over 14 days old and ban reproductive cloning.

Daniel Avila, associate director of public policy for the Massachusetts Catholic Conference, said legislators are expected to vote on the partial veto sometime during the week. The MCC, the public policy arm of the Catholic Church in Massachusetts, has encouraged Catholics to contact their legislators and speak out against the bill.

"The issues raised by the governor are critical issues, and we would support the amendments," Avila told The Pilot.

Avila called the amendments “very positive improvements,” but stressed that the bill itself is still a problem even if all the amendments are approved by Congress, especially because it still endorses research on embryos.

Avila admits that despite Romney’s promise to veto the bill if it is sent back to him, legislators will likely return it in its entirety. In both the House and Senate the embryonic stem-cell research bill was approved by over the two-thirds majority necessary to override a veto.

Still, Avila remains hopeful.

"We did have three legislators in the House switch their votes unexpectedly when the House sent the final version to the governor last week. We're still urging people to put constituent pressure on their legislators and see if that bears any greater fruit," he said.

AP materials contributed to this report