The controversy around embryonic stem cell research has resurfaced in the us, this time pitting president George W Bush against many other Republican leaders. The us house of representatives passed a bill on May 24, 2005, allowing public funding for such research through the National Institutes of Health (nih), under the us Department of Health and Human Services. The proposed law gives couples, who have undergone fertility treatment, the choice to donate their extra embryos for research. But Bush, who had banned federal funding for this purpose in 2001, opposes the bill, which now goes to the senate. He has threatened to exercise his presidential veto, a prerogative he has never used during his presidency, to block it.

Embroynic stem cells are extracted from embryos and can develop into virtually any cell of any human organ. These cells can be directed to grow into tissues (bone marrow, neural tissue or muscle) and used to treat degenerative diseases like spinal cord injury, stroke, heart disease, diabetes, arthritis, Alzheimer's disease and Parkinson's disease. The embryo is destroyed in the process. This is what Bush objects to: "There is no such thing as a spare embryo. Every embryo is unique and genetically complete, like every other human being