BEIJING--The attendance of both the former bishop of Hong Kong and an adviser to Taiwan’s leader at this week’s funeral for Pope Emeritus Benedict XVI highlights the Vatican’s uneasy relationship with communist-ruled China.

The Chinese government, which does not have formal diplomatic ties with the Vatican, has not commented on Benedict’s death and did not appear to be sending anyone to Thursday’s service.

Pope Francis, who succeeded Benedict in 2013, has tried to mend fences with Beijing, moving beyond the harder line approach of his predecessor to sign an agreement in 2018 on the appointment of bishops in China. At the same time, the Vatican has maintained diplomatic relations with Taiwan instead of China, one of only a handful of governments that still do.

Cardinal Joseph Zen, the former Hong Kong bishop going to the funeral, has harshly criticized the agreement on bishops. In a blog post in Italian this week, he praised Benedict, who elevated Zen to cardinal in 2006.

“He could not accept any compromise,” wrote the 90-year-old Zen, who was arrested last year after he fell afoul of Hong Kong authorities over his participation in a now-silenced democracy movement.

Zen said he was grateful for a letter Benedict wrote to China’s Catholics in 2007, in which he invited them to unite under his authority, and for his efforts in setting up a powerful commission to handle the Chinese church’s affairs.

China’s ruling Communist Party closely controls organized religion, which it sees as a potential threat to its monopoly on power. People are allowed to worship in institutions that abide by party rules. Some Christians have set up underground churches, which are considered illegal and harassed by authorities.

The agreement on Catholic bishops has been renewed twice, most recently for two more years last October. A month later, a feud broke out over the installation of an auxiliary bishop in Jiangxi province, which the Vatican does not recognize as a diocese.

Full details of the agreement have never been made public but Francis has said he has final say in the selection of bishops. The Vatican describes the deal as an imperfect one that it hopes will eventually lead to better conditions for Catholics in China.

Zen was detained in May on suspicion of colluding with foreign forces under a national security law that Beijing imposed after massive pro-democracy protests in 2019. He has yet to be formally charged, but he and five others were fined in a separate case in November for failing to register a now-defunct fund set up to help arrested protesters.

Police confiscated his passport after he was arrested, so he had to apply in court for permission to leave the city earlier this week.

Taiwan is sending former official Chen Chien-jen, a devout Catholic, as a special envoy to Benedict’s funeral. He is a scientist who was minister of health and later vice president under President Tsai Ing-wen from 2016 to 2020.

“The symbolic meaning of sending Chen is greater than sending the current ambassador to the Vatican,” said Chang Chia-lin, a professor of religious studies at Aletheia University in Taiwan.

Benedict was not as warm toward China as his predecessor, Pope John Paul II, Chang said. The Vatican’s turn toward China began under Benedict, who reached out to Beijing, although unsuccessfully.

John Paul viewed both Taiwan and Hong Kong as a connecting bridge to Chinese Catholics.

China and Taiwan split in 1949 during a civil war in which the communists came to power and the defeated nationalists fled to the island of Taiwan.

China still considers Taiwan part of its territory and won’t establish diplomatic relations with nations that have official ties with the self-governing island. Only 14 governments, including the Vatican, recognize Taiwan instead of China.

The lack of ties makes it difficult for China to send a representative to a papal funeral, said Francesco Sisci, a China-Vatican relations expert at Settimana News, a Catholic research center in Italy.

China did not send anyone to John Paul’s funeral in 2005, though a Foreign Ministry delegation paid respects to his body privately in a little-known episode, Sisci said.

That could happen again, though an ongoing COVID-19 outbreak in China could complicate the situation, he said.