ST. LOUIS -- In his three years as St. Louis archbishop, the Most Rev. Raymond Burke has taken on a presidential contender, a pop star, Missouri politicians and even parishioners.

American bishops regularly speak against public policies that run contrary to Roman Catholic teaching, but Burke stands out for his hard line on those who oppose church teachings, no matter how high-profile or popular they are.

"I know I have to teach. I know I have to be clear about the church's position," Burke said. "If that means that national media takes an interest in it, then that's something that I have to accept. But that's certainly not my object in my activity."

Burke set off a national debate in 2004 when he said he would deny Holy Communion to presidential hopeful John Kerry because the Catholic Democrat supports abortion rights. Only a few other U.S. bishops went as far as Burke; most said they opposed using the sacrament as a sanction.

In April, Burke resigned as board chairman for the Cardinal Glennon Children's Foundation because of a benefit-concert appearance by singer Sheryl Crow, who supports abortion rights and embryonic stem-cell research. Crow declined interview requests.

And last month, a local Catholic high school revoked an invitation to U.S. Sen. Claire McCaskill, D-Mo., to speak at her daughter's commencement from the institution. The senator also supports abortion rights and embryonic stem-cell research. Burke backed the school's decision, though he said he had no direct hand in it.

A McCaskill spokeswoman has said the senator understands her positions differ from those held by the church, but she's made peace with them.

The archbishop, a genial-looking man with a soft conversational voice, said he must serve as a moral guide.

"The most pressing issue is the secularization in society," Burke said. "The church finds herself more and more in a prophetic role of calling into question trends in society."

Burke, 58, came to St. Louis after years in Rome.

A graduate of the Pontifical Gregorian University in Rome and a student of canon law, Burke spent five years in service to the highest court in the church, the Supreme Tribunal of the Apostolic Signatura. In 1995, he was installed as bishop of La Crosse, Wis., then in 2004, was elevated to St. Louis, home to 550,000 Catholics.

Burke said he has been surprised by the strong reaction to his declarations. Kerry has said he shares the church's opposition to abortion, but did not feel it was appropriate to legislate personal religious beliefs.

"To me, it didn't seem like anything very radical to say that a Roman Catholic who persists in a public way in fostering legislation that permits procured abortion should be denied Communion," Burke said.

Burke has his critics.

In 2005, the archbishop excommunicated the six-member board of St. Stanislaus Kostka, a traditionally Polish parish, after the members refused to end an arrangement that dated back to the late 19th century giving them authority over parish finances.

Burke also excommunicated the Rev. Marek Bozek, who was brought in by the parish.

Bozek said the archbishop is a good man, but inflexible.

"For him, I think compromise is a dirty word," Bozek said. "Unfortunately, the church is moving from having a dialogue into a monologue."