China's head of religious affairs said that Beijing is willing to have constructive dialogue with the Vatican but stressed that Catholics should "hold up high the flag of patriotism" and adapt Catholicism to Chinese society.

Wang Zuo'an, the director of the State Administration for Religious Affairs, made the remarks Tuesday at a meeting of China's official Catholic Church, which includes bishops, priests and lay Catholics, state media reported.

Beijing insists that the party-controlled Chinese Catholic Patriotic Association has the authority to appoint Chinese bishops, a right that the Holy See says belongs to the pope alone. This dispute over bishop nominations is the most vexing stumbling block preventing the re-establishment of diplomatic relations.

China severed relations with the Holy See in 1951 after the Communists took over, and the officially atheistic government closed churches and imprisoned priests, some for decades. Worship is officially allowed only in state-authorized churches outside the pope's authority, although many of China's estimated 12 million Catholics are thought to attend underground churches.

Wang said the Chinese government hoped that the Vatican can adopt a flexible and pragmatic attitude, and take concrete actions to create favorable conditions for improving relations, according to the official Xinhua News Agency. No details were given of what actions Beijing expects.

The ruling Communist Party has long feared that opposition to its rule could be spread by religious and other civic groups outside its control. In May last year, President Xi Jinping called for religions to adapt to Chinese society, which he termed the "sinicization of religion."

On Tuesday, Wang stressed the importance of patriotism within religion and "pushing ahead with the sinicization of Catholicism."

Pope Francis said earlier this year that Beijing and the Vatican have resumed working groups on the naming of bishops issue and that he is "optimistic" for an agreement, but that it will take time.

Just last week, the Vatican said it was saddened that the ordination of two new Chinese bishops was marred by the presence of a bishop ordained without the pope's consent.

It also said it was awaiting the outcome of this week's meeting of the Chinese Catholic Church and hoped it would give Catholics in China confidence in the Vatican-China dialogue.