VATICAN CITY -- When Pope Benedict XVI told a crowd in St. Peter's Square in April that the Virgin Mary "silently followed her son Jesus to Calvary, taking part with great suffering in his sacrifice, thus cooperating in the mystery of redemption and becoming mother of all believers," most listeners probably heard nothing remarkable in the statement.

After all, devotion to Mary is a pervasive element of the Catholic faith, and one of the features that most clearly distinguishes it from Protestantism.

Yet for one group of devotees, Benedict's statement was a milestone -- a sign that he had moved one step closer to granting their wish for a new dogma on Mary's contribution to human salvation.

At least 7 million Catholics from more than 170 countries, including hundreds of bishops and cardinals, have reportedly signed petitions urging the pope to proclaim Mary "the Spiritual Mother of All Humanity, the coredemptrix with Jesus the redeemer, mediatrix of all graces with Jesus the one mediator, and advocate with Jesus Christ on behalf of the human race."

In other words, the Virgin Mary -- though always subordinate to and dependent on the will of Christ -- plays an active, unique and irreplaceable role in helping her son deliver mankind from sin and death.

Proponents say that such a statement would represent the culmination of the church's traditional teaching on Jesus' mother, and bring the world untold spiritual and material benefits.

But critics of the proposed dogma say it would exaggerate Mary's true importance and undermine efforts toward unity with other Christian denominations.

The idea of Mary as Christ's collaborator in the redemption of humanity is deeply rooted in Catholic tradition, said Monsignor Arthur B. Calkins, an American priest working at the Vatican who has written extensively on the subject.

"The church has been meditating on this role for two millennia," Calkins said in an interview, "and so the Holy Spirit continues to draw forth what is there already in seed."

According to Mark Miravalle, a professor of theology at Franciscan University of Steubenville, Ohio, the new dogma would mean the "climax of the `Age of Mary'," a period that began in 1830 with apparitions of the Virgin in France, and witnessed papal proclamations of her Immaculate Conception (1854) and bodily Assumption into heaven (1950).

Supporters of the dogma of Mary Coredemptrix began petitioning the Holy See in the 1920s, Miravalle said, but it was in the 1990s that the movement drew millions of supporters and its goal began to appear within reach.

Pope John Paul II publicly used the term "Coredemptrix" at least six times in his pontificate, and at one point Miravalle predicted that he would proclaim the dogma before the millennial year of 2000.

The professor now believes that John Paul was persuaded not to act by advisers who feared that the new dogma would pose an obstacle to ecumenical dialogue.

At least one non-Catholic participant in that dialogue says such fears were well-founded.

"Anglicans require that any dogma be provable from Scripture," said the Rev. William Franklin, academic fellow at the Anglican Centre in Rome and a visiting professor at the Vatican's Pontifical University of Saint Thomas Aquinas.

Anglican ecumenists are still struggling to reconcile their beliefs with the papal dogmas of the Immaculate Conception and the Assumption, Franklin said. "Making a new Marian dogma would complicate the journey toward full communion between our two churches," he said.

Proponents of the dogma insist that it would actually promote ecumenism by dispelling any ambiguities about Catholic doctrine.

"This would bring new clarity that Catholics do not adore Mary as a goddess," Miravalle said. "It would underscore what Catholics do believe -- that she is your spiritual mother -- but at the same time that she is not the fourth person of the Blessed Trinity."