The Vatican is involved in a peacekeeping mission in an effort to end the war between Russia and Ukraine, Pope Francis said on Sunday, declining to elaborate.

“I’m willing to do what needs to be done. There is a mission now underway, but that mission is not yet public. When it becomes public, I will reveal it,” the pope told reporters on the plane back to the Vatican after a three-day visit to Hungary.

“I think peace is always achieved by opening channels. You can never achieve peace through blockades… This is not easy,” he stressed.

The pontiff added that he discussed the situation in Ukraine with Hungarian Prime Minister Viktor Orbán and with Metropolitan Hilarion, representative of the Russian Orthodox Church in Budapest. “In these meetings (…) we talked about all these things. Everyone is interested in the road to peace,” he said.

Since the start of Russia’s invasion of Ukraine 14 months ago, Francis has appealed almost weekly for peace and has repeatedly expressed a desire to act as a mediator between Kiev and Moscow, but his offer has not led to any significant progress.

Ukrainian Prime Minister Denis Smykhal met with the pope at the Vatican on Thursday and said he discussed with the pontiff a “peace formula” proposed by Ukrainian President Volodymyr Zelensky. The Ukrainian prime minister stressed that he also invited Francis to visit the Ukrainian capital.

The 86-year-old pope has previously said he wants to visit Kiev as well as Moscow on a peacekeeping mission.

Francis also spoke today about his health adventure following his hospitalization at the end of March. As he announced, at the end of the general audience on Wednesday, March 29, he felt an intense pain.

“I didn’t lose consciousness but I had a high fever and at 3 in the afternoon the doctor told me to go to the hospital immediately,” he said.

“It was acute pneumonia in the lower part of the lung. (…) My body responded well to the treatment, thank God,” the pope said. He was released from the hospital on April 1.