Pope Benedict XVI made his strongest push for reuniting Catholics in China with the Vatican Saturday when he urged Beijing to restore diplomatic ties and honor religious freedom.

In a letter to Chinese Roman Catholics posted on the Vatican website, the pope called on Catholics attending state-run churches and those participating in the underground churches to unite. He also urged the officially atheist Chinese government to negotiate on the appointment of Chinese bishops and the restoration of official relations between the country’s Catholics and the Holy See.

“I realize that the normalization of relations with the People’s Republic of China requires time and presupposes the good will of both parties,” the pope wrote. “For its part, the Holy See always remains open to negotiations, so necessary if the difficulties of the present time are to be overcome.”

The Chinese government broke ties between its Roman Catholics and the Vatican in 1951 – two years after the communist government took power. The registered state-run Catholic churches recognize the Pope as a spiritual leader, but accepts the government’s appointment of bishops – an act which has cause resentment between the two powers.

The underground Catholic Church, however, remains loyal to Rome and refuses to be controlled by the state.

In a note accompanying the letter, the Vatican also noted that it was prepared “at any time” to move its diplomatic representative from Taiwan to Beijing as soon as an agreement is reached, according to The Associated Press.

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The Vatican hopes to reach a compromise relationship like the one in place in neighboring communist Vietnam, according to AP. There, the Vatican proposes names of bishops and the government selects from the list.

Benedict also made a significant move towards reconciliation by revoking the 1988 Vatican restrictions on contacts with clergies of the official churches in China.

China’s foreign ministry, although refusing to say whether the Pope’s letter had been received by Chinese authorities, expressed hope for better relations with the Vatican. Yet he noted that China will maintain its negotiation stance.

“China will stick to the two principles to improve and develop our relations with the Vatican,” said ministry spokesman Qin Gang, according to Agence France-Presse. “Our position has not changed.”

The two principles before normalization can take place are: the Holy See must cut ties with Taiwan and vow to not use religion to interfere in China’s internal affairs.

Taiwan split from China in 1949 after the communist takeover, leaving a hostile relationship between the two nations until this day.

There are an estimated 8-12 million Chinese Catholics in China, according to Reuters.