Pope Francis warned on Monday against a resurgence of nationalist and populist movements and criticized countries that try to solve the migration crisis with unilateral or isolationist actions.
The pope, speaking to diplomats in an annual speech known informally as his "state of the world" address, suggested such movements and closed-door policies were turning the clock back 100 years to the dangerous period between the world wars.
Relationships within the international community "are experiencing a period of difficulty, with the resurgence of nationalistic tendencies," he said, making dialogue between countries and hurting the most vulnerable members of society, including migrants.
Populist anti-immigrant parties made gains in a number of countries last year, including Italy, France, the Netherlands, Hungary, Brazil, and Poland.
In the United States, a partial government shutdown entered its third week as President Donald Trump has pledged not to bend in his demand for a wall along the southern border with Mexico.
In his hour-long speech, Francis several times mentioned the League of Nations, which was set up after World War One to promote peace but failed to stop the nationalist and populist movements that helped lead to World War Two.
"The reappearance of these impulses today is progressively weakening the multilateral system," he told envoys from 183 countries in the speech, which touched on the situation in many countries.
While migration has led to diffidence and unilateral actions by governments, particularly in Europe and North America, the international community has a duty to defend refugees and migrants, he said.
"I do not believe that partial solutions can exist for so universal an issue," he said.
Francis praised the United Nations' Global Compact on Migration, which set objectives for how the movement of people can be managed. The United States, Italy, Hungary, and Poland are among nations that boycotted the meeting in Morocco last year.
The pope again condemned the arms trade and possession of nuclear weapons, lamenting that past efforts at nuclear disarmament had given way to "the search for new and increasingly sophisticated and destructive weapons."
He called for a more decisive commitment to combating global warming and for "rethinking our relationship with our planet".
Calling sexual abuse of children "one of the plagues of our time", he said a meeting of key bishops at the Vatican in February would aim to "shed full light on the facts and to alleviate the wounds caused by such crimes".