People gather at Saint Peter's square before Pope Francis's Angelus prayer at the Vatican in August.
CNN  — 

The Vatican says it has extended its controversial agreement with China over the appointment of bishops for another two years.

Details of the agreement, which was struck in 2018, have never been made public. It has been criticized by some Catholic officials as well as by US Secretary of State, Mike Pompeo.

But the Vatican said on Thursday that the deal “is of great ecclesial and pastoral value” and said it “intends to pursue an open and constructive dialogue for the benefit of the life of the Catholic Church and the good of Chinese people.” Officially, there are about 6 million Catholics in China.

Prior to 2018, Beijing had long insisted on having the final say on all bishop appointments in mainland China, while the Holy See maintained that only the Pope has such authority.

The eventual agreement brought to an end decades of tension between the Vatican and China, which severed diplomatic ties with the Holy See in 1951 after an alleged, and often discredited, assassination plot against Chinese leaders involving a Catholic priest.

The ruling and officially atheist Communist Party had long portrayed foreign religious institutions such as the Catholic Church as hostile forces responsible for the country’s suffering and humiliation during the late 19th and early 20th centuries.

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.

In October, Secretary Pompeo said in an article in a conservative Catholic magazine that the agreement with China compromised the moral authority of the Vatican.

The Vatican’s statement said there had been “good communication and cooperation” with China and that they intended “to pursue an open and constructive dialogue for the benefit of the life of the Catholic Church and the good of the Chinese people.”

The future of the deal had appeared murky earlier this year, when a report said China was suspected of hacking the Vatican.

CNN’s Daniel Burke contributed reporting