Burke, 59, will be the first American to serve as prefect of the Supreme Tribunal of the Apostolic Signatura. The job usually comes with a cardinal's red hat, which would add another American to the conclaves that elect popes.

Burke has led the charge among a handful of U.S. bishops to discipline Catholic politicians who stray from church teaching. In 2004, he told Democratic presidential nominee Sen. John Kerry he could not receive Communion in St. Louis because of his support of abortion rights and in 2007 said he would refuse Communion to then-Republican candidate former New York City mayor Rudy Giuliani for the same reason.

The new post will allow Burke to leave his conservative imprint on the wider church, leading a court that has final say on administrative disputes but also marriage annulments and church closings.

"The appointment should make pro-choice and same sex marriage Catholic politicians very nervous," warned the Rev. Thomas Reese, a senior fellow at the Woodstock Theological Center at Georgetown University.

Burke's five-year tenure in St. Louis has been brief but fiery. After publicly rebuking Kerry and other prominent Democrats, last year he said ministers who distribute Communion are "held, under pain of mortal sin, to deny the sacraments to the unworthy."

Earlier this year, he excommunicated three women who were ordained as priests against church rules, and also said he would deny Communion to basketball coach Rick Majerus at St. Louis University for his support of abortion rights, same sex marriage and stem cell research.

He also forbade Sen. Claire McCaskill, D-Mo., from speaking at her daughter's graduation ceremony at a Catholic high school because of her record on abortion, and resigned from a Catholic children's charity after the group featured singer Sheryl Crow, who supports abortion rights, at a medical center fundraiser.

He also told Catholics not to celebrate St. Patrick's Day on the holiday because it fell during Holy Week.

Burke becomes the second American to take on a prominent Vatican post. Cardinal William Levada, the former archbishop of San Francisco, now heads the church's doctrinal office, a post he inherited from Pope Benedict XVI.

Burke replaces Italian Cardinal Agostino Vallini, who was named Friday as the pope's vicar general for the Diocese of Rome — effectively, the city's acting bishop.

The Signatura hears appeals of decisions by lower church courts and administrative bodies, and settles jurisdictional disputes. According to Reese's book "Inside the Vatican," "Only about half a dozen cases a year are heard by the panel of cardinals and bishops, and these cases take about three years to be processed."

Burke has been a member of the tribunal since July 2006.

If Burke is named a cardinal as expected, he will join 20 other U.S. cardinals, 14 of whom are currently under the age of 80 and thus eligible to vote for the next pope.