ROME – Catholic women seeking to become priests denounced the church's ban on female ordination as sexist and unjust, bringing their campaign to the Vatican on Wednesday during a worldwide gathering of bishops.

The small group of women representing Catholic organizations from around the world marched across the Tiber River close to St. Peter's Square, some wearing signs with the names of prominent women in the early days of the Roman Catholic Church.

“Ordain Women! Ordain Women!” the woman chanted.

Aisha Taylor, the executive director of the Women's Ordination Conference in the United States, said the women wanted to call attention to the issue during the synod, a meeting of 253 bishops under way. She said the group handed out fliers in St. Peter's Square and delivered a petition to the Vatican's police.

But the Vatican is not likely to drop its long-standing prohibition on women in the priesthood.

In May, the Vatican insisted that it is properly following Christian tradition by excluding women from the priesthood and issued a new warning that women taking part in ordinations will be excommunicated.

The church has always banned the ordination of women by stating that the priesthood is reserved for men. The decree issued in May was explicit in its reference to women.

Pope Benedict XVI led the doctrinal office before becoming pontiff in 2005. Like his predecessor, Pope John Paul II, he has consistently rebuffed calls to change traditional church teachings on divorce, abortion, euthanasia, gay marriage and the requirement that priests be male and celibate.

Taylor conceded that no discussion on women's ordination was likely to open – and certainly not at the synod, a gathering convened by the pope when he deems necessary, and devoted this time to discussing the relevance of the Bible for contemporary Catholics.

Taylor did take the presence of 25 women, either as observers or experts, at the synod as a mildly encouraging sign. But – with the women representing just 10 percent of the synod and none having a vote – she said it was not enough.

“The exclusion of women from the priesthood is a grave injustice in our church ... (and) a blatant example of sexism,” she told reporters in Rome. “Even though leaders have come out saying no, and it's over and over again, I do believe that cannot continue for too many decades.”

The Vatican's firmness on the issue has dashed the hopes of women seeking to be priests but also of Catholics who see that as an option for a church struggling to recruit men. It has also raised fears that women might abandon the Roman Catholic Church for other branches of Christianity that allow female priesthood.

In March, the archbishop of St. Louis excommunicated three women – two Americans and a South African – for participating in a woman's ordination. They were part of the Roman Catholic Womenpriests movement, which began in 2002.