HONG KONG (AFP) - Hong Kong Cardinal Joseph Zen has earned a reputation as a fighter - and the octogenarian's latest battle pits him against Vatican officials and Beijing over a deal he believes would devastate the Catholic Church.

The former Bishop of Hong Kong is well-known in the city for his vocal opposition to political suppression and his support for democratic reform.

But 86-year-old Zen's latest cause goes to the heart of his beliefs about the Catholic Church and what it should represent.

It comes as the Vatican moves closer to a historic agreement with China over the major stumbling block of who ordains bishops - a deal Zen fears would backfire against the underground Catholic Church in the mainland which is routinely persecuted by Chinese authorities.

"For several decades the government has made it hard for them but they remained loyal to Rome and the pope. And now they're asked to surrender?" Zen said in an interview with AFP.

"Some people in China might revolt."

China's roughly 12 million Catholics are divided between a state-run association whose clergy are chosen by the government and an unofficial church which swears allegiance to the pope.

The Chinese Communist Party is officially atheist and religious groups are tightly controlled by the state. Catholic and Protestant churches have been demolished in recent years and Christian clergy detained, as traditional Western congregations shrink.

Beijing and the Vatican severed diplomatic relations in 1951 and although ties have improved as China's Catholic population grows, they have remained at odds over the designation of bishops.

But a Vatican source told AFP last month that in a framework agreement still under negotiation with China seven state-appointed bishops would be recognised, although no time frame was specified.

'HEARTBREAKING'

Zen has accused Vatican officials of "selling out" to China and was chastised by Vatican spokesman Greg Burke for "fostering confusion and controversy" with his remarks.

Burke also denied Zen's allegation that the pope was not informed of actions he would not agree with.

Zen, who had a private audience with the pope in January during which he raised the bishops issue, believes senior Vatican officials are pushing their own political agendas.

"The pope doesn't know the Chinese Communist Party, but these officials do. They are not ignorant," he says.

Vatican number two Pietro Parolin was central to warming relations with the communist government of Vietnam and has spoken of the need for unity in the Catholic Church in China.

But Zen is highly sceptical of any goodwill from Beijing, recalling how some unofficial clergy in the mainland have been jailed for decades and died in prison.

He also cites his own experience teaching in state-run mainland seminaries for seven years.

Bishops there were under close surveillance and "led by the nose", he says.

"It was heartbreaking." .

CHORUS OF DISCONTENT

Hong Kong has long served a critical role in supporting China's underground churches and many of the city's Catholics have joined the growing chorus against rapprochement between Beijing and the Vatican.

Zen says he was driven to become more vocal about human rights after Britain handed Hong Kong back to China in 1997.

After becoming Bishop of Hong Kong in 2002, he fiercely opposed the local pro-Beijing government's anti-subversion bill the following year, which was shelved after hundreds of thousands took to the streets in protest.

"I speak up because I feel I have to, not because I like to," Zen says, occasionally banging the table and waving his arms for emphasis.

He lives at the Salesian House of Studies, a training school for clergy, where he first arrived in 1948 at the age of 16 from his hometown in Shanghai.

The complex perches on a hillside in eastern Hong Kong Island and Zen fondly remembers the old views of Victoria Harbour, before the surrounding land was reclaimed.

Made a cardinal in 2006, he retired from his post as bishop three years later but still takes part in the city's pro-democracy protests, these days manning the donation box instead of marching.

A lung virus which led to his hospitalisation in 2016 seems not to have dented his energy or spirit.

Zen says if the deal between the Vatican and Beijing is finally signed, he would have to accept it out of respect for the pope.

But for now, he will continue to fight.

"At a certain point they know it's impossible to eradicate religion," says Zen of China's communist government.

"So they must control it if they cannot eradicate it."