He hopes it will cool a situation that had become "too hot" and posed the risk of nuclear devastation.
Pope 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, Pope Francis also said he was ready to meet U.S. 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 re-assert 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.
"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.
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