The landmark deal between China and the Vatican is a win for Beijing, giving official recognition to bishops appointed by the government despite a crackdown on religion, and potentially softening the ground for full diplomatic relations after 67 years of estrangement, analysts said.
The two sides signed a provisional agreement on Saturday on who gets to name senior churchmen, an issue that has bedevilled ties for decades, and China quickly said it hoped for an improvement in relations.
That is bound to mean consequences for self-ruled Taiwan, which Beijing considers a renegade province, and which has watched helplessly in recent years as its giant neighbour has picked off its few remaining diplomatic partners.
With its outsized international influence, the Vatican is the most important of Taiwan's 17 remaining friends, and its only European partner.
The agreement on bishops makes no mention of diplomatic relations, but some see the writing on the wall.
"It's difficult not to see this as the first step towards a switch," said Jonathan Sullivan, a China expert at the University of Nottingham.
"It's not on the cards yet, but Beijing has made no secret of its desire to poach Taiwan's most important remaining ally."
Ying Fuk-tsang, a professor of divinity at the Chinese University of Hong Kong, said Beijing is bound to use any new leverage to seek the Holy See's recognition.
The current Taiwan government has taken a toughened line against Beijing, which knows that turning the Vatican would be "a major blow to Taiwan's diplomacy," Ying said.
- 'Sinicisation' of religion -
Beijing and the Vatican severed ties in 1951, two years after the Communist Party seized power.
The party tolerates no alternative power centres and a decades-long impasse has played out over who presides over the now roughly 12 million-strong Catholic faithful -- communist-approved prelates or those who preach to "underground" pro-Rome churches.
Since taking office in 2013, Pope Francis has sought to improve ties with China.
As part of the deal, the pope recognised seven Beijing-appointed bishops. No other details were disclosed.
The apparent Vatican concession is striking because it comes as China is waging a broad religious crackdown.
President Xi Jinping has moved aggressively to tighten the Communist Party's grip on all aspects of society, including worship.
Top leaders have recently called for the "Sinicisation" of religion, code for greater party control.
In China's remote western Xinjiang region, UN estimates say one million members of Muslim minorities are held in internment camps where rights groups say they face communist indoctrination.
Christian worshippers and clergy in central China told AFP recently that "illegal" churches were being raided or bulldozed, and religious materials confiscated.
Churches have been required to display the national flag while removing religious imagery from public-facing spaces, and paperwork seen by AFP shows clergy are being pressured to divulge personal information about parishioners.
Underground clergy told AFP they remain fearful because the agreement does not mention safeguards for them or their followers, with one priest saying worshippers "doubt the sincerity" of the government.
An official priest in close contact with the underground community said that while the deal solves the problem of the seven bishops, it says nothing about how future bishops will be appointed.
"And it cannot solve the real problem and situation of the church."
- 'Not a zero-sum game' -
China's religious crackdown has drawn growing overseas criticism, with US Secretary of State Mike Pompeo on Friday deploring "awful abuses" in Xinjiang.
He added that Christians were suffering too as authorities are "closing churches, burning Bibles" or forcing them "to renounce their faith."
But Francesco Sisci, an Italian Sinologist at China's Renmin University, said a rapprochement could provide the Vatican with now-scarce leverage in China because it will now get at least some recognition from Beijing.
"It's not a football match, it's not a zero-sum game. Both sides hopefully gained a lot in this," Sisci said.
"It is true that dozens of churches are being torn down, at least partially. But thousands more are standing or being built."
"It will be not be easy, but if the Vatican doesn't try to help now, when should it?"