Pope Francis holding a rosary as he left at the end of his weekly audience in St Peter’s Square at the Vatican on Wednesday. Photo: Reuters

A global assembly of Roman Catholic bishops is shaping up as the first major showdown of Pope Francis’s papacy, with conservative and progressive cardinals strongly disagreeing with each other ahead of its start on Sunday.

The two-week synod on the theme of the family will be attended by more than 250 people: nearly all of them bishops of the 1.2 billion-member Church and also 13 married couples.

It will prepare the way for a larger gathering of Catholic clerics next year and could become a milestone in the clash between conservatives and liberals over the future direction of a Church that the Pope has insisted must become less bureaucratic and theologically esoteric.

The synod, the first since Pope Francis’s election in March 2013, is seen as a test case for him and his vision of a Church he wants to be closer to the poor and suffering and not “obsessed” by issues such as homosexuality, abortion and contraception.

Conservatives say marriage, divorce rules cannot change

The run-up to the meeting has been dominated by a rare public feud between cardinals centred on whether the Church should modify teachings that ban Catholics who have divorced and then remarried in civil services from receiving communion.

For Catholics, a second marriage without an often lengthy Church annulment of the first amounts to adultery and anyone remarried in a civil ceremony cannot receive communion at Mass unless they refrain from sexual relations with a new partner.

That issue has emerged as the most likely candidate for possible reform after Pope Francis ordered a worldwide survey of Catholics and heard that many ignored Church teachings on birth control, sex before marriage or acceptance of homosexuality.

Cardinal Walter Kasper, a German the Pope has called one of his favourite theologians, has argued that the Church must find ways of showing mercy to people whose first marriages have failed and who want to remain an integral part of the Church. But even the suggestion of change has galvanised conservatives, including a handful of senior Vatican officials.

Cardinal Kasper says the Church needs a “paradigm change” to seek a solution to the problem of divorced and remarried Catholics and suggested that each case should be studied separately and couples possibly given personal dispensation from the rules. He accused conservative critics of attacking him in order to undermine their real target – the Pope. He accused conservatives of political manoeuvring and using fear tactics to block potential change.

Cardinal Kasper’s most vocal critic is Cardinal Leo Raymond Burke, a Vatican-based American arch-conservative, who, along with four other like-minded cardinals, launched a pre-emptive strike by publishing a book, Remaining in the Truth of Christ, defending the status quo on rules for the divorced and re-married.