President Bush faces a congressional challenge to his veto on the use of human embryos in stem cell research on Thursday.
But the pro-research lobby in the House of Representatives looks set to fall short of the two thirds majority it needs to override the Presidential veto.
Commentators say Democratic midterm gains in the the House were not enough to swing the vote away from moral objectors who believe taxes should not be used to create new human stem cell lines; a process which means the embryo will not develop.
Senate leaders say they have a pro-stem cell funding majority large enough nullify the President, but without the House they are powerless.
Bush used his power of veto for the first time in the summer after the then Republican majority House of Representatives and Senate approved measures to fund research into new lines. Responding to a reporter's question as to why the unprecedented action would be taken, Bush spokesman Tony Snow said: "The simple answer is he thinks murder's wrong."
Left unobstructed, the bills would have overturned his original 2001 decision against funding, announced in one of his first White House TV addresses.
Lobbying has continued in earnest on both sides of the debate since the veto. At December's midterm elections many Republican deserters cited the administration's dogmatic stance against a science at such an early stage. Despite the beating Bush took on this and other issues, the White House reaffirmed its stance prior to today's vote and indicated it would apply the veto again.
Sensing victory perhaps, the administration issued a report entitled "Advancing Stem Cell Science without Destroying Human Life". It said: "The stem cell debate is only the first in what will be an onrushing train of biotechnology challenges in our future. We must establish a constructive precedent here for taking the moral dimensions of these issues seriously."
The emotive metaphor of biotechnology as an "onrushing train" echoes Bush's own Brave New World misgivings, which he sounded in his 2001 TV address. He said: "Researchers are telling us the next step could be to clone human beings to create individual designer stem cells, essentially to grow another you, to be available in case you need another heart or lung or liver."
The anti-embryonic stem cell stance taken by the US has meant effort which would have been spent on investigating the properties of these most powerful of all cells has been spent on identifying alternative sources. At the weekend much media coverage was devoted to the discovery of less potent stem cells in amniotic fluid, for example.
In the UK, meanwhile, the Royal Society today gave a guarded welcome to government plans to look more closely at the issue of combining animal and human embryos new cell lines non-therapeutic purposes. The research would see human nuclear DNA inserted into the empty "shells" of rabbit embryos (which would still contain some rabbit DNA in their energy-producing mitochondria).
Royal Society president Martin Rees said: "It is unfortunate that this judgement has been delayed, however the decision to consult widely to reach a consensus on this complex issue is a sensible one. It is now vital that the consultation takes account of our current understanding of the science and the potential future benefits."
"Stem cell research is still in its early stages and it is essential that we do not close off avenues for potential development before they have been fully explored."
A sentiment which Parkinson's disease, spinal injury and Alzheimer's sufferers in the US and elsewhere would empathise with, no doubt. ®