Langhorne, Pa. ? First lady Laura Bush defended her husband’s policy on embryonic stem cell research Monday, calling Democratic rival John Kerry’s criticism “ridiculous” and accusing proponents of overstating the potential for medical breakthroughs.

“We don’t even know that stem cell research will provide cures for anything — much less that it’s very close” to yielding major advances, Bush said.

The first lady weighed in on the highly charged political and scientific issue on the third anniversary of Bush’s decision to limit federal funding of embryonic stem cell research to only the 78 stem cell lines in existence Aug. 9, 2001.

Religious groups oppose the scientific work in which culling of stem cells kill the embryos, equating that with abortion, and had urged Bush not to be the first president to fund the research — even with limits.

Proponents of the science, including former first lady Nancy Reagan and 58 Democrats and Republicans in the Senate, argue that it could lead to cures to diseases such as diabetes and Alzheimer’s. Former President Reagan suffered from the latter for a decade before his death June 5.

With polls showing overwhelming support for stem cell research, Kerry has promised to give scientists more freedom. He has used the word ban to describe Bush’s actions when what the president has done is limit the research.

“That’s so ridiculous,” Laura Bush said in an interview with The Associated Press. “It’s one of the myths that start during a campaign.”

Unusually combative, the first lady said Kerry was trying to make a political issue out of her husband’s policy “without saying what’s right. I imagine he knows better.”

Kerry’s running mate, Sen. John Edwards of North Carolina, said Monday marked “a sad anniversary” because the Bush administration “put restrictions in place that dramatically undermine our efforts to find cures for diseases.”

Edwards, in a conference call with reporters, said Kerry would reverse Bush’s policy, invest $100 million for research for the science.