ROME — Pope Francis and his diplomats have been quietly pouring energy into negotiations with the Chinese government that could help end a decades-long dispute over control of the Catholic Church in the country.

But as signs of a possible breakthrough have emerged — how bishops get ordained has long been a sticking point — some Catholics are worried. They fear that the Vatican, in its eagerness for a deal, could betray clerics and parishioners who have illicitly practiced their faith for decades and risked arrest and persecution by worshiping in the so-called underground church. They are also alarmed that a deal could end the independence for which the underground church has long stood.

The dissension escalated on Friday as the retired archbishop of Hong Kong, Cardinal Joseph Zen, intensified his criticism of the talks, saying that a reconciliation could result in 12 million Chinese Catholics being effectively put in a Communist-controlled “cage.” He has accused church bureaucrats of “selling out” Chinese Catholics, and warned, “A church enslaved by the government is no real Catholic Church.”

Cardinal Zen did not attack the pope directly, but called Cardinal Pietro Parolin, the pope’s second-in-command, “a man of little faith.” Another prelate has mocked one of the pope’s close collaborators as living “in Wonderland” for his depiction of China as a country uniquely in sync with the church’s values.