Adding fuel to the House debate was the announcement last week by South Korean researchers who, funded by their government, produced human embryos through cloning and then extracted their stem cells -- a major advancement in the quest to grow patients' own replacement tissue to treat diseases.

Proponents of embryonic stem cell research, the subject of the House bill sponsored by Democrats Mike Castle and Diana DeGette, say it carries great promise in the fight against diseases such as Alzheimer's and Parkinson's.

It is controversial because the process destroys the embryo -- a practice its opponents say is immoral. President George W. Bush on Friday promised to veto the legislation if it passes Congress.

J.J. and Trey Jones of Houston, who "adopted" their month-old son Trey as an embryo, are appearing on Capitol Hill with the bill's opponents.

"We believe frozen embryos are pre-born children who deserve a chance to be born," the couple wrote on their Web site.

Those lobbying for the measure include Dana Reeve, widow of actor Christopher Reeve, who died last year after suffering a spinal cord injury in 1995.

"This is not a baby, it's not an embryo, it is pre-embryonic. This is something that would not, once it was implanted, turn into a human being," Dana Reeve said Sunday on ABC's "This Week."

Adding fuel to the House debate was the announcement last week by South Korean researchers who, funded by their government, produced human embryos through cloning and then extracted their stem cells -- a major advancement in the quest to grow patients' own replacement tissue to treat diseases.

Bush, who has not vetoed any bills during his five years in office, said the announcement represents his deepest concerns about making cloning acceptable. He said he would veto the Castle-DeGette bill if it reaches his desk. Several senators said Sunday they expect the Senate to consider the bill this year.

The bill would lift Bush's 2001 ban on the use of federal dollars for research using any new embryonic stem cell lines.

"I made very clear to Congress that the use of federal money, taxpayers' money, to promote science which destroys life in order to save life -- I'm against that," Bush said. "Therefore, if the bill does that, I would veto it."

House Republican leaders have offered an alternative bill that would encourage stem cell research using blood from umbilical cords. Joined by several House members who are doctors, their lobbying effort includes first-person stories from people with diseases like sickle cell anemia that were corrected using this method.