Pope Francis is on Wednesday to release a much-anticipated text about the Amazon, which is not expected to open up the priesthood to married men in the region despite an appeal from a historic Vatican meeting of bishops last year.

The text could however make damaging the environment a sin, one of the recommendations of the bishops from the nine-country Pan-Amazonian region.

The bishops' three-week "synod" in October highlighted challenges such as the destruction of the rainforest, the exploitation of indigenous peoples and a scarcity of priests.

They called on the Argentine pontiff to open the priesthood to married men in the Amazon, as well as to give women a greater role to play and to make damaging the environment a sin, in a region threatened by massive deforestation and mining.

The pope's text, which is to be released around 1100 GMT, will respond to those calls and could have repercussions not only for the vast, isolated territory, but the whole of the Roman Catholic Church.

Last year's synod brought some 184 bishops to the Vatican, over 60 percent of whom hailed from the Amazon region.

Together with representatives of indigenous peoples, experts and nuns, they discussed a multitude of regional concerns, from climate change to poverty, land-grabbing, mercury-polluted waters and violence against women.

The most hotly debated question was whether or not to allow "viri probati" -- married "men of proven virtue" -- to join the priesthood in remote locations, where communities seldom have mass due to a lack of priests.

It would not be necessary to rewrite Church law; the bishops simply asked Francis for an exemption to the rules -- like the one already granted to married Anglican pastors who convert to Catholicism.

The synod suggested ordaining as priests "suitable and esteemed men of the community" who had "a legitimately constituted and stable family".

A Vatican meeting in October discussed challenges such as the destruction of the rainforest and the exploitation of indigenous peoples
A Vatican meeting in October discussed challenges such as the destruction of the rainforest and the exploitation of indigenous peoples AFP / Andreas SOLARO

But the ultra-conservative wing of the Catholic Church -- particularly in Europe and North America -- has spoken out strongly against the idea, warning that making exceptions could pave the way to the abolition of celibacy globally.

US bishops who met the pope on Monday said the document was unlikely to change priestly celibacy rules or the role of women.

"He didn't say much about the two pressing issues, about the ordination of women deacons and married priests," Salt Lake City bishop Oscar Solis told the US Catholic News Service.

"The pope, very gently and very calmly, said, 'You know, this point was really not a big point in that synod,'" said Archbishop John Wester of Santa Fe, New Mexico, without specifying if he was referring to married priests or women deacons.

"I don't even think at this point that it's something we're going to move on because I haven't sensed that the Holy Spirit is at work in that right now," the pope reportedly said.

In January 2019, Francis said he did not believe that optional celibacy should be allowed, while conceding "some possibilities for far-flung places" such as Pacific islands or the Amazon.

Last month former pope Benedict, who retired in 2013, issued a defence of clerical celibacy in a book written with arch-conservative Cardinal Robert Sarah.

"The conjugal state concerns man in his totality, and since the service of the Lord also requires the total gift of man, it does not seem possible to realise the two vocations simultaneously," Benedict wrote.

The synod also urged the Argentine pope to make "the acts and habits of pollution and destruction of the harmony of the environment (an) ecological sin" -- or the breaking of a divine law.

The Church should lead the battle against "our culture of excessive consumption", the bishops urged, saying: "We must reduce our dependence on fossil fuels and the use of plastics."