HONG KONG (Reuters) - A Hong Kong cardinal who has spearheaded opposition to the Vatican’s rapprochement with China called on Thursday for the Pope’s secretary of state to step down, saying any deal with Beijing would amount to a betrayal of the Catholic faith.

FILE PHOTO: Former head of the Catholic Church in Hong Kong, Cardinal Joseph Zen, 86, attends a news conference in Hong Kong, China February 9, 2018. REUTERS/Bobby Yip/File Photo

The Vatican and China have been in advanced talks this year to forge what would be an historic breakthrough and precursor to a resumption in diplomatic relations after 70 years, with Secretary of State Pietro Parolin among the chief negotiators.

The Vatican may send a delegation to China before the end of this month. If the meeting goes well, the two could reach an agreement on the appointment of bishops, a Chinese state-run newspaper reported earlier this week.

Cardinal Joseph Zen, the most senior Catholic cleric on Chinese soil, said he believed the two sides were making a “secret deal”, although he acknowledged he had no connection with the Vatican and was “completely in the dark”.

“They’re giving the flock into the mouths of the wolves. It’s an incredible betrayal,” he said.

He described Parolin, the highest ranking diplomat in the Vatican, as someone who despised heroes of faith.

“He should resign,” Zen told Reuters at his home on a wooded hillside on Hong Kong island.

“I don’t think he has faith. He is just a good diplomat in a very secular, mundane meaning.”

Zen, who at times knocked his knuckles on the table to make a point, stopped short of calling on Pope Francis to step down, saying: “I would not come out to fight the Holy Father, that is my bottom line.”

The Vatican did not immediately respond to a request for comment on Zen’s remarks.

At a time when the Vatican is also under pressure for purportedly covering up a sex abuse scandal in the United States, with one archbishop even calling for the Pope to resign, Zen suggested this China deal would further add to the Church’s vulnerability.

“The consequences will be tragic and long lasting, not only for the church in China but for the whole church because it damages the credibility. Maybe that’s why they might keep the agreement secret.”

China’s roughly 12 million Catholics are split between an underground Church that swears loyalty to the Vatican, and the state-supervised Catholic Patriotic Association.

The potential deal has divided communities of Catholics across China, some of whom fear greater suppression should the Vatican cede greater control to Beijing, but others want to see rapprochement.

Zen said he believed only half the underground church in China would accept a deal and was concerned how the remainder might react.

“I’m afraid they may do something irrational, they may make rebellion,” said 86-year-old Zen, a former bishop of Hong Kong and the most outspoken critic of the Pope’s China strategy.

Pope Francis has rejected criticism that the Holy See may be selling out Catholics to Beijing’s communist government.

Zen said he believed any deal with atheist China would deal a significant blow to Pope Francis’ credibility.

“It’s a complete surrender. It’s a betrayal (of our faith). I have no other words, said Zen.