Pope Francis announced the information, as Reuters reported.
"There is a mission in course now but it is not yet public. When it is public, I will reveal it," he told reporters after a three-day visit to Hungary.
"I think that peace is always made by opening channels. You can never achieve peace through closure. ... This is not easy," the Pope added.
He recalled that he had spoken about the situation in Ukraine with Hungarian Prime Minister Viktor Orban.
"We spoke of all these things. Everyone is interested in the road to peace," Francis said.
On April 12, Pope Francis called on world leaders to use reason, not weapons, to resolve differences, recalling the Cold War of the 1960s between Washington and Moscow.