President Bush defended restrictions on stem-cell research on Wednesday and reaffirmed support for nuclear-arms development, but Democratic challenger John Kerry accused Bush of putting ideology over science.

Bush pledged to keep restrictions on federal funding for stem-cell research involving human embryos, despite pressure from hundreds of scientists and both parties in Congress. The restrictions limit federal cash to batches of human cells taken from embryos before August 9, 2001.

'I am committed to pursuing stem-cell research without crossing a fundamental moral line,' Bush said. He said the federal government last year had spend $25 million on embryonic stem-cell research, and nearly $191 million for research involving adult stem-cells.

Kerry, a Massachusetts senator, said he would lift Bush's 'ideologically driven restrictions' on stem-cell research but ensure rigorous ethical oversight.