Pope says he can’t visit Ukraine or Russia due to knee problems

"Now I cannot go because after the trip to Canada there’s been a bit of a setback with the knee recovery and the doctor banned it, saying ‘Before Kazakhstan you cannot travel,'" Francis said, referring to religious leaders gathering in Kazakhstan from September 13 to 15.

"But I have been maintaining contact over the telephone … Among all of us, something could be done. I’m following (the situation) with my pain and my prayers. But the situation is really tragic,” he continued. “I always believe that by having a dialogue, we advance."

Francis said that he wanted to visit Ukraine but that Moscow was on the top of his list so that he could promote peace.

Francis told Reuters that he had suffered a "small fracture" in his knee when he took a misstep.

Francis is set to appear in the new Kazakh capital of Nur-Sultan to attend the seventh Congress of Leaders of World and Traditional religions.