The Bilateral diplomacy of the Holy See is unique in world affairs in that it has little or nothing to do with the things with which diplomats typically occupy their time: trade issues, security matters, visas.

Rather, the reason why the Vatican engages in bilateral diplomacy is to secure the freedom of the Catholic Church to be itself in the countries with which the Holy See has, or wishes to have, diplomatic relations. To be sure, in crisis situations, the Holy See’s representative in a crumbling or violence-ridden state can also serve as an honest broker amidst contending local parties, or a voice for persecuted Catholic communities, or a channel for humanitarian assistance. Whatever the situation, the first task of the pope’s representative to another sovereignty is to help maintain free space for the Church’s evangelical, sacramental, educational and charitable missions, all of which are essential to what it means to be “the Catholic Church” in any human situation.

This unique character can create unique challenges; two such challenges today involve Cuba and China.

In Cuba, the role played by Vatican officials and the archbishop of Havana, Cardinal Jaime Ortega, in facilitating the recent agreement between the U.S. and Cuba to restore full diplomatic relations has significantly raised the stakes for how the local Church in Cuba, and the Holy See, play their respective hands in the last days of the Castro regime.

Those “last days” may, alas, be a matter of years; still, that Castroism has no future seems obvious to everyone except the brothers Castro. Some Catholic leaders in Cuba are understandably concerned to use what openings may now be available to build up the Church’s infrastructure in that long-suffering island.

But if that build-up involves a kind of relationship with the present Cuban regime that precludes strong, vocal and visible Catholic support for those hard-pressed Cuban human rights activists who form the core of the post-communist Cuban civil society of the future, the evangelical mission of the Church in a post-Castro Cuba could be seriously imperiled.

Building-while-resisting, and thus helping accelerate the change toward a post-Castro future – that is the challenge for Cuban Catholicism, which will face the daunting task of re-converting Cuba in the 21st century. The local Church should be sup- ported in both aspects of that work, the building and the resisting, by the Holy See.

Then there’s the new thaw in the Holy See’s relations with the People’s Republic of China (PRC). It’s no secret that senior Vatican diplomats have long sought full diplomatic exchange at the ambassadorial level with the PRC; the theory is that such diplomatic recognition will give the Catholic Church a more secure place at the table as China determines its future. But here, too, there are evangelical concerns to be considered.

Full diplomatic relations between the Holy See and the PRC would require the Vatican to sever diplomatic ties with Taiwan – the first Chinese democracy in that ancient country’s 5,000-year history. And while there is nothing inexorable about a transition to democracy in mainland China, there does seem something inherently unstable about communist regimes, especially if they’ve been sitting atop a substantial middle class that’s not going to accept political disenfranchisement indefinitely.

If and when a Chinese democratic revolution happens, too close a relationship with a faltering communist regime that has a history of persecuting Christians and pro-democracy activists could be an obstacle to the evangelization of China, which, when it fully opens itself to the world, will be the greatest field of Christian mission since the Europeans came to the western hemisphere in the 16th century.

We may be sure that Evangelical Protestants and Mormons, who will not be burdened by having had diplomatic relations with the PRC, are already thinking hard about their missions in a post-communist China. That, too, should concentrate Catholic minds on how the alleged benefits of a deal between the Vatican and the current regime in Beijing are to be weighed against the potential perils to the new evangelization in a post-communist China.

George Weigel is a senior fellow of the Ethics and Public Policy Center in Washington D.C.