ROME – When Pope Francis delivered an impassioned plea for multilateralism in his annual speech to diplomats on Jan. 7, it was also a clear, if indirect, appeal for respect and participation in the United Nations, which is the planet’s leading forum for multilateral diplomacy.

The speech marked the latest chapter of the odd-couple relationship between the Vatican and the UN, alternating between strong basic support and occasionally titanic battles.

Francis himself captures that dynamic in miniature. The Argentine pontiff has often criticized what he calls an “ideological colonization” on the part of some UN bodies pushing the use of contraception or gender ideology. Yet his frequent engagement with the UN on key issues such as migration and climate change is also an example of Francis’s keen interest in building bridges, seeing the UN as both a partner and a platform for that effort.

On Jan. 7, Francis said “an indispensable condition for the success of multilateral diplomacy is the good will and good faith of the parties, their readiness to deal with one another fairly and honestly, and their openness to accepting the inevitable compromises arising from disputes.”

“Whenever even one of these elements is missing, the result is a search for unilateral solutions and, in the end, the domination of the powerful over the weak,” he said, and lamented that the international community and multilateralism as a whole “are experiencing a period of difficulty, with the resurgence of nationalistic tendencies at odds with the vocation of the international organizations to be a setting for dialogue and encounter for all countries.”

Francis also noted how 2019 marks the 100th anniversary of the foundation of the League of Nations, a precursor to the UN established after the carnage of the First World War, saying it stirred a different approach to international affairs.

The Vatican’s interest in the UN goes all the way back to the beginning, since the Holy See had representatives on the ground when the charter for the new planetary body was signed in San Francisco on Oct. 24, 1945.

Nations who ratified the charter included China, France, the Soviet Union, the United Kingdom and the United States, among others. At the time, then-Bishop Angelo Giuseppe Roncalli, now Saint Pope John XXIII, was serving as the papal envoy to France. Having been appointed to the post in December 1944, he would have likely had a role in discussions during the charter’s drafting process.

Currently one of two permanent non-member observer states to the UN, the other being Palestine, the Holy See since the beginning has consistently sought involvement in UN affairs in the push for reconciliation after the Second World War, and in the current global climate characterized by conflicts Francis has often referred to as a third world war being fought “piecemeal.”

Among the biggest areas of divergence between the UN and the Holy See are matters related to international family rights, such as access to birth control as a matter of women’s health and the push for contraception as a means of population control.

In his 2015 environmental encyclical Laudato Si, Francis criticized nations who “instead of resolving the problems of the poor and thinking of how the world can be different, some can only propose a reduction in the birth rate.”

He denounced the fact that population control is often proposed as a solution to problems stemming from poverty and maintaining a sustainable consumption of the earth’s resources, and condemned the fact that developing nations often receive pressure from international organizations who make economic assistance “contingent on certain policies of ‘reproductive health.’”

These issues were points of debate long before Francis, forming the most heated debate topics during a 1994 UN conference on world population in Cairo, for instance, and a 1995 UN World Conference on Women in Beijing, both of which saw a strong push from Western nations for abortion and forms of artificial birth control.

In Cairo, then-Bishop Renato Martino, who at the time was the Holy See’s permanent observer to the United Nations and was head of the Vatican delegation to the population conference, said in an interview with Vatican Radio that certain parts of the final declaration posed a “serious threat to the future of mankind,” as the wording all but endorsed abortion as a means of population control. He accused the UN of bowing to wealthy Western nations and called the draft of the document “neo- colonialist.”

Similarly, in Beijing the Vatican and several other nations took issue with wording in the final document surrounding sexual and reproductive rights, and in their final presentation reiterated their position against abortion and artificial contraception.

In both conferences the Vatican found natural allies in the Islamic world, with many Muslim nations boycotting the Cairo conference and backing the Vatican in their push for axing controversial wording on abortion and birth control from the agenda at both.

Even now the Vatican continues to take issue with the United Nations Population Fund (UNFPA), whose mission is self-defined as being “to deliver a world where every pregnancy is wanted, every childbirth is safe and every young person’s potential is fulfilled.”

Among other things, the UNFPA supports “reliable access to modern contraceptives sufficient to benefit 20 million women a year,” above all in developing nations, which the Vatican and Francis have consistently condemned.

However, regardless of the disagreements, the Vatican’s relationship with the UN has been overwhelmingly collaborative, and they have sought to engage with nations on key areas of human interest.

In the current papacy, these areas have largely revolved around climate change and migration, with the Holy See giving firm and vocal support to several initiatives in line with the UN’s own agenda.

On the climate issue in particular the Vatican has played a larger-than-usual role. Retired Pope Benedict XVI was a major advocate for environmental protection, and despite the condemnation of population control in Francis’s Laudato Si, the document was largely published to influence global discussion on the issue, as it was published just before the Paris COP21 climate summit.

Francis has also been outspoken on the issue of migration, speaking out on the issue in major speeches at both the EU headquarters in Strasbourg and the UN headquarters in New York. For the past 18 months the Holy See has also been a vocal advocate of the global UN compact on migration, which was adopted in Marrakech, Morocco in December.

In the lead-up to the summit, the Vatican drafted 20 pastoral action points for safe, orderly and dignified migration, and urged nations to sign the non-binding compact.

In a sense, the Vatican’s fundamentally pro-UN stance probably shouldn’t be any surprise.

The Catholic Church was global long before anyone thought to coin the term “globalization,” and has always seen national differences relative and subordinate to the common good and a shared humanity.

Given the global platform offered by the UN, it’s understandable why popes have consistently engaged with it as a tool to get their message across to a worldwide audience and to put their agenda on the international radar.

And if Francis’s tenure is any indication, the match, however troubled at times, isn’t likely to end anytime soon.