Pope Francis said on Saturday a third country, such as Norway, should try to mediate in the dispute between North Korea and Washington, to cool a situation that had become "too hot" and posed the risk of nuclear devastation.
Francis said he believed "a good part of humanity" would be destroyed in any widespread war.
Speaking to reporters aboard the plane taking him back from Cairo, Francis also said he was ready to meet US President Donald Trump when he is in Europe next month but that he was not aware that Washington had made a request for a meeting.
In answer to a question about the tensions between the United States and North Korea, Francis said the United Nations should reassert its leadership in world diplomacy because it had become "too watered down".
"I call on, and will call on, all leaders, as I have called on leaders of various places, to work to seek a solution to problems through the path of diplomacy," he said about the North Korea crisis.
Francis spoke after North Korea test-fired a ballistic missile shortly after US Secretary of State Rex Tillerson warned that failure to curb Pyongyang's nuclear and ballistic missile programmes could lead to "catastrophic consequences".
In a fresh development, it was reported that US warships were carrying out drills off the Korean coast.
Appealing for calm, the Pope said: "There are so many facilitators in the world, there are mediators who offer themselves, such as Norway for example," he said in his customary freewheeling news conference with reporters at the end of each trip.
"It [Norway] is always ready to help. That is just one but there are many. But the path is the path of negotiations, of a diplomatic solution," he said in the discussion, which lasted about 30 minutes.
Norway secretly negotiated an agreement between Israel and the Palestinians known as the Oslo Accords in the early 1990s.
The pope expressed his deep concern over the crisis, saying: "This question of missiles in [North] Korea has been brewing for more than a year but now it seems the situation has become has become too hot."
He said: "We are talking about the future of humanity. Today, a widespread war would destroy – I would not say half of humanity – but a good part of humanity, and of culture, everything, everything.
"It would be terrible. I don't think that humanity today would be able to withstand it."
Trump is due in Sicily on May 26 and 27 for a meeting of the heads of the world's richest nations. The White House has not yet said if he would be stopping in Rome to meet the pope, which would be an unusual omission for a visiting head of state.
Asked if he would be meeting Trump, the pope said he had not yet been informed if a request had been made, but added: "I receive every head of state who asks for an audience."