Pope Francis is to meet one of the most senior spiritual leaders of the world's Sunni Muslims at the Vatican on Monday, according to a pontifical spokesman.
Sheikh Ahmed al-Tayeb, the grand imam of Cairo's Al-Azhar University, the most prestigious institution in Sunni Islam, will meet the Pope at St Peter's.
Father Federico Lombardi told AFP: "This audience is being prepared and has been scheduled for Monday. It will be a first."
Al-Tayeb has been an outspoken opponent of Islamist extremism, saying after the Paris attacks that terrorism was not an expression of any Abrahamic faith. It was rather an "intellectual and psychological disease" that used religion as a front, he said.
He has also met the Archbishop of Canterbury at Lambeth Palace and stressed their common commitment to building "bridges of peace".
In a significant address at a conference at Al-Azhar in February 2015, al-Tayeb called for the reform of Islamic teaching saying: there had been "a historical accumulation of excessive trends" that had led some people to embrace a misguided form of Islam".
One of the factors which has rendered Islamic State's brand of ideology so toxic is its habit of pronouncing other Muslims as apostates. Al-Tayeb said: "The only hope for the Muslim nation to recover unity is to tackle in our schools and universities this tendency to accuse Muslims of being unbelievers."
He referred to "terrorist groups... who have opted for savage and barbaric practices".
Relations between the Vatican and the Muslim world soured under Francis' predecessor Benedict XVI after Benedict was perceived to have described Islam as a violent religion. However, they have improved under Francis, who has kept inter-faith dialogue at the top of his agenda.