The state's four Roman Catholic dioceses will use the first Sunday of Advent to launch a campaign aimed at keeping Catholics from signing the petition, and to teach them the Catholic view of the issue.
A coalition of business interests, universities and patient groups is leading the petition drive and has begun airing advertisements. Some believe its success could help fuel a national movement to protect stem cell research through state constitutional amendments.
John J. Leibrecht, bishop of the Springfield-Cape Girardeau diocese, said the effort was a way to combat well-financed proponents of the amendment and a mainstream media that dismisses the Catholic viewpoint.
The bishops also have asked every Catholic parish in Missouri to hold an educational event to discuss the topic.
The Catholic church opposes human embryonic stem cell research because it requires the destruction of human embryos, which church leaders contend is akin to abortion.
In a recent column in his archdiocesan newspaper announcing the campaign, St. Louis Archbishop Raymond Burke wrote about the "intrinsic evil" of embryonic stem cell research.
"To sign a petition favoring the initiative is to promote the culture of death which tragically besets our nation and constitutes a cooperation in the destruction of human lives at their very beginning," he wrote.
Former Sen. John Danforth, honorary co-chair of the Missouri Coalition for Lifesaving Cures and an ordained Episcopal priest, said the archbishop is attempting to impose his own theology on an issue that affects more than just Catholics.
"The archbishop has clearly staked out a religious position," Danforth said. "But it's not everybody's religious position", reported AP.