JEFFERSON CITY, MO. ? The battle over embryonic stem cell research moved into the pews Sunday, as Roman Catholic priests across Missouri urged churchgoers to oppose a petition seeking a constitutional amendment that would protect the controversial work.

The petition drive was announced last month by a group of business leaders, patient advocates and researchers as a response to legislative efforts to ban a type of stem cell research known as therapeutic cloning.

Missouri’s Catholic dioceses oppose it, and they urged their priests statewide to begin a campaign Sunday aimed at keeping Catholics from signing the petition.

The petition seeks to put a measure on the 2006 ballot that would amend the state constitution to state that stem cell research, therapies and cures allowed under federal law also are permitted in Missouri. The measure would prohibit human cloning, defined as the effort to create a baby by implanting an embryo that wasn’t fertilized by sperm.

The petition drive must have about 145,000 valid signatures by May 9 to secure a spot on the November 2006 ballot.