By Christian Fraser
BBC News, Rome
Vietnamese and Vatican officials are meeting this week to discuss a road map towards re-establishing full diplomacy.
The Vatican and Vietnam have held 15 rounds of talks
After decades of tension, there has been rapid improvement in the negotiations between the Vatican and the Communist-run country.
Full relations may be restored within several months.
In Rome, the outspoken Hong Kong Cardinal, Joseph Zen, welcomed the steps and said he hoped the negotiations with Vietnam could be used as a model to improve relations with China.
However, he said so far the government in Beijing was refusing to honour many of the promises it had made.
The Vatican has indicated for a long time that it wants to establish normal diplomatic relations with Beijing even at the cost of moving its embassy from Taiwan.
But it will not compromise on the tradition dictating that only the Pope can appoint bishops.
Last year Beijing, in its state-backed Church, frustrated Vatican diplomacy by ordaining three bishops without Pope Benedict's approval.
Cardinal Zen says that shows the concessions the Vatican has made are still not being reciprocated by the Communist government, and he has called for tougher negotiations.
"The Vatican is always eager to have the situation normalised. It is the policy of the Chinese government which has to be changed.
"We really hope the Chinese government see the point that it's high time we come to negotiate and get a conclusion," Cardinal Zen said.
Beijing's ties with the Vatican were broken in 1951, after the Communists took power in China. Worship is only allowed in government-controlled churches.
Cardinal Zen has been criticised for his attacks on the human rights abuses in China, but he makes no apologies.
He says he speaks for as many as 10 million Catholics who are estimated to belong to the so-called "underground congregations" loyal to Rome.
"Whatever I say, I say from the point of our Catholic faith, and I'm saying things from my understanding of the feeling of our people in China.
"Sometimes I speak in the name of the underground Church; sometimes I speak in the name of the people in the open Church.
"So if anybody is really interested in really understanding, in knowing the truth... they should welcome what I am saying," Cardinal Zen said.
Pope Benedict has made improving relations with China a key item on his agenda, and Cardinal Zen will no doubt play an important role.
The cardinal has asked to be released from his post as Bishop of Hong Kong so he can concentrate more on these negotiations.