George Bush's decision on Friday to fund limited stem cell research drew both applause and criticism. It was also seen as sharp politics that allowed him to hurdle the toughest decision yet of his presidency.
Under considerable pressure, Mr Bush said he would allow federal funds to be used for research on existing lines of embryonic stem cells, where those embryos had already been destroyed. He said he would not allow any cloning to create new embryos.
Mr Bush said in a televised address late on Thursday evening: "I have made this decision with great care and pray that it's the right one.
"I have concluded that we should allow federal funds to be used for research on these existing stem-cell lines where the life-and-death decision has already been made."
Reaction to the decision from the most committed and extreme camps was strong. Scientists said the decision did not go far enough and would slow up vital research into diseases such as Parkinson's and Alzheimer's. The Catholic Church and some of the far-right "pro-life" groups condemned the decision for what they said was "encouraging the destruction of human life".
The one real exception to this was the National Right to Life Committee which said it was "delighted that President Bush's decision prevents the federal government from becoming a party to any further killing of human embryos for medical experimentation".
Stem cells are early or primitive cells which have the ability to transform themselves into many other types of cells. There are several sources for such cells, most notably human embryos.
Mr Bush, speaking from his ranch at Crawford, Texas, told the nation that there were more than 60 genetically diverse stem cell lines already in existence around the world.
The research he would fund would be limited to stem cells from those existing lines as long as they had been removed from embryos that were surplus or abandoned by couples at fertility clinics, and were normally destroyed.
Federal rules would require that the donors give consent and did not benefit from the donation of the cells.
Mr Bush said: "As I thought this issue through, I kept returning to two fundamental questions: First, are these frozen embryos human life and therefore something precious to be protected? And second, if they're going to be destroyed anyway, shouldn't they be used for a greater good, for research that has the potential to save and improve other lives?"
Scientists said the decision would hold up research on diseases and conditions that affected hundreds of thousands people. Dr John Gearhart, a researcher at the John Hopkins University in Baltimore, said: "The limitation the president has put on this is going to delay, substantially, the progress we need to make to bring these types of therapies to the bedside."
The actor Michael J Fox, who suffers from Parkinson's disease and is a vocal campaigner for stem cell research, said he was glad of the funding but felt it did not go far enough. He said: "We do have a little bit of a feeling that he's put us on the launch pad and he's given us clearance for take-off but we have real questions about the quality and quantity of fuel he has given us."
The actor Christopher Reeve, who suffers from a paralysing spinal cord injury, said: "I think it is a step in the right direction. I think what needs to happen is that the matter ought to go before Congress and that legislation should be introduced to adopt the Clinton guidelines that were put in place a couple years ago that allow broader research in this."
Opponents said Mr Bush had gone too far. Bishop Joseph Fiorenza, president of the US conference of Catholic Bishops, said: "The trade-off he has announced is morally unacceptable. The Federal government, for the first time in history, will support research that relies on the destruction of some defenceless human beings for the possible benefit of others."Reuse content