The war in Ukraine is driven by the interests of several "empires" and not just of Russia's, Pope Francis said in an interview published on Friday.

Francis said the conflict was fuelled by "imperial interests, not just of the Russian empire, but of empires from elsewhere".

He expressed a readiness to talk to Russian President Vladimir Putin to call for peace.

Francis, who is 86 and marks the 10th anniversary of his election on March 13, also said he would resign if he got too tired and lost the capacity to govern the Roman Catholic Church.

Last month, he had said that papal resignations should happen in only exceptional circumstances.

His predecessor Benedict XVI, who died on Dec. 31 aged 95, became the first pontiff to resign in about 600 years when he stepped down in 2013.

Asked what would lead him to make the same decision to quit, Francis said: "A tiredness that doesn't make you see things clearly. A lack of clarity, of knowing how to evaluate situations".

Francis said he was "a bit ashamed" to use a wheelchair due to a knee ailment.

"I am old. I have less physical resistance, the knee (problem) was a physical humiliation, even if the recovery is going well now," he said.