Pope Francis has called on all nations to support dialogue to ease tensions on the Korean peninsula and to work for a legally-binding ban on nuclear weapons.
In his "State of the World" address, the pontiff also repeated his call for a two-state solution between Israelis and Palestinians and respect the "status-quo" of Jerusalem following US President Donald Trump's decision to recognise the city as Israel's capital.
The pope addressed envoys from more than 180 countries.
It comes a day before North and South Korea are due to hold talks expected to address North Korea's participation in the Pyongchang Winter Olympics. Some diplomats see this as a possible opening for discussions on other topics such as humanitarian issues and divided families.
What did Pope Francis say?
"It is of paramount importance to support every effort at dialogue on the Korean peninsula, in order to find new ways of overcoming the current disputes, increasing mutual trust and ensuring a peaceful future for the Korean people and the entire world."
"Nuclear weapons must be banned," Francis continued, quoting a document issued by Pope John XXIII at the height of the Cold War.
"There is no denying the conflagration could be started by some chance and unforeseen circumstance," he continued.
Noting tjat the Holy See was among 122 states that last year agreed a United Nations treaty to ban nuclear weapons, he called for a "serene and wide-ranging debate" on disarmament.
The US, Britain, France and others boycotted the talks that lead to the treaty, instead pledging commitment to a decades-old Non-Proliferation Treaty.
Climate change and migration
Francis called for a "united effort" to remain committed to the 2015 Paris accord on reducing carbon emissions.
Having made defence of migrants and refugees a major plank of his pontificate, Francis warned against "stirring up primal fears" of newcomers.
"There is a need, then to abandon the familiar rhetoric and start from the essential consideration that we are dealing, above all, with persons," he said.
Migration has become a top political issue in countries including the United States, Italy and Germany.