Pope Francis and the head of the Russian Orthodox church, who backs the war in Ukraine, will not meet when both men attend a gathering of religious leaders in Kazakhstan next month, RIA news agency cited a senior Orthodox official as saying on Wednesday.

Francis, due to be in the capital Nur-Sultan from 13th-15th September to attend the VII Congress of Leaders of World and Traditional Religions, has said in several recent interviews he hopes to meet with Patriarch Kirill when in Kazakhstan.

But Bishop Anthony, the Russian church's second most powerful bishop, told RIA there was no question of the two religious leaders meeting on the sidelines.

"It (a meeting) must be an independent event by virtue of its importance," said Anthony, in charge of foreign relations, who held talks with Francis in early August. Francis has met Kirill once before, in Cuba in 2016.

Kirill, a close ally of President Vladimir Putin, has given enthusiastic backing to the invasion of Ukraine.

In June, Francis implicitly accused Russia of "armed conquest, expansionism and imperialism" in Ukraine.