WASHINGTON (CNN) -- Missouri GOP Sen. Jim Talent, locked in a close race with State Auditor Claire McCaskill, told CNN Thursday he does not want to criminalize stem cell research as a controversial ad starring Michael J. Fox suggests.

The embattled incumbent told CNN's Wolf Blitzer he has supported the research in the past, but is against the specific stem cell ballot initiative in his state because he says it funds the destruction of human embryos.

"The allegations in the commercial are false," Talent said on the 'The Situation Room.' "I'm not saying anything with regard to Mr. Fox's intent. No, I've supported that research over the years. Now, I'm not comfortable crossing a line we've never crossed before and funding research--funding research that involves the destruction of a human embryos."

The stem cell issue has become a lighting rod in this race since actor Michael J. Fox, stricken with Parkinson's disease, appeared in an emotional ad last week advocating for the controversial research.

For CNN's coverage of the midterm elections, check out America Votes 2006