Stem cells will be at the top of the agenda for the US Senate when it returns on Tuesday with supporters of the research hoping they can change the president's mind on the issue and opponents hoping to have a say about their stand.
The Senate will consider two bills, one virtually identical to a bill vetoed by President George W. Bush last year that would have expanded and encouraged federal funding of human embryonic stem cell research.
The other is a compromise measure worked out by Republicans Sen. Johnny Isakson of Georgia and Norm Coleman of Minnesota. It would encourage stem cell research on embryos that have naturally lost the ability to develop into fetuses, such as those that have died "naturally" during fertility treatments.
The compromise bill also would support the creation of a bank of stem cells taken from amniotic fluid and placentas - two recently discovered potential sources.
This bill replaces last year's alternative sponsored by Kansas Republican Sam Brownback, which would ban human embryonic stem cell research and encourage research using other types of stem cells.
The House of Representatives passed a bill in January that would expand federal funding of stem cell research, which is now restricted by Bush to batches available as of August 2001. But the bill does not have enough supporters to override a second presidential veto.
It is not clear how much support there is for either Senate bill, although opponents of human embryonic stem cell research, such as Brownback, have signalled they will vote for the compromise bill. They also said they were looking forward to making use of up to 20 hours of scheduled debate.
Stem cells are the body's master cells, giving rise to all the tissues and cells that make up a living creature. Scientists are working with stem cells from a variety of sources to try to cure diseases such as diabetes and Parkinson's, and perhaps someday regenerate organs and tissue.
VARIOUS SOURCES:
Stem cells taken from days-old human embryos appear to be especially powerful and many scientists consider them among the most promising sources of stem cell research. But most researchers stress that it is important to study all types and sources of stem cells.
The United States has no restrictions on research funded by private sources or by states and several, including California, are actively funding embryonic stem cell research.
Opponents say it is unethical to experiment on human embryos and especially wrong to destroy them. "Without an understanding that life begins at conception and that an embryo is a nascent human being, there will always be arguments that other uses, take-overs and make-overs of embryos are justified by potential scientific and medical benefits," the White House wrote in a report issued in January.
The issue transcends the abortion debate with conservative Republicans who oppose abortion such as Utah Sen. Orrin Hatch backing broader federal funding of embryonic stem-cell research.
Polls show the US public consistently supports embryonic stem cell research, especially using embryos left over from fertility treatments.
"We got a super-majority under the Republican-controlled 109th Congress," said Sean Tipton of the American Society of Reproductive Medicine, which lobbies in support of embryonic stem-cell research.
Tipton said the current Democratic-controlled Senate will be even friendlier. "When the Senate passes this bill, the president is going to be under incredible pressure to acknowledge that the science has changed and to acknowledge that the American people support this research," he said in a telephone interview.