(CNN)A long-expected, controversial deal between the Chinese government and Catholic leaders in the Vatican has sparked opposition, including inside the Church itself.
The provisional agreement, which will see the Vatican recognize the legitimacy of bishops appointed by the Chinese government, comes at a time when the ruling Communist Party is cracking down on "illegal" Christian groups in the country.
Officially, there are about 6 million Catholics in China, although the real number could be more than twice that when counting followers in so-called underground, or unlicensed churches, according to a researcher with the Holy Spirit Study Center in Hong Kong.
The deal, which is part of Pope Francis's vision to expand the Catholic Church's following across the world, would help the Vatican gain access to potentially millions of converts across China, the world's most populous nation.
But critics have questioned why the church, historically a defender of human rights and Christian values, would willingly join forces the increasingly authoritarian Chinese government, which is officially atheist.
Speaking to Reuters, Catholic Cardinal Joseph Zen of Hong Kong said the Church's deal was an "incredible betrayal" and accused the Vatican of "giving the flock into the mouths of the wolves."
Previously Chinese Catholic bishops in the state-sanctioned church were not appointed by the Pope, which had been a key sticking point between Beijing and the Vatican since relations broke down in 1951.
Amnesty International China Researcher Patrick Poon told CNN the agreement created serious concerns for freedom of religion in China in the future.
"Such an agreement will effectively set a very bad precedent for other religions (in China) ... It will put Catholics under a lot of pressure," he said.
While the details around the agreement remain vague, including who would have the final say on appointments, Chinese state media was effusive in its support for the proposal.
The Chinese Catholic Patriotic Association and Bishops' Conference of the Catholic Church in China said in a statement in state media they "wholeheartedly supported" the deal.