VATICAN CITY: Pope Francis is to meet the grand imam of Cairo's Al-Azhar at the Vatican on Monday in an unprecedented encounter between the leader of the world's Catholics and the highest authority in Islam.

Sheikh Ahmed al-Tayeb, who heads the mosque and seat of learning considered the most prestigious institution in Islam, will have an audience with the leader of the world's 1.2 billion Catholics, Vatican spokesman Federico Lombardi told AFP.

"This audience is being prepared and has been scheduled for Monday," he said. "It will be a first".

The hugely symbolic visit comes against the backdrop of a recent improvement in relations between the two faiths after serious tensions during the time of Francis's predecessor, Benedict XVI.

Ties were badly soured when the now-retired Benedict made a September 2006 speech in which he was perceived to have linked Islam to violence, sparking deadly protests in several countries and reprisal attacks on Christians.

Dialogue resumed in 2009 but was suspended again by Al-Azhar in 2011 when Benedict called for the protection of Christian minorities after a bomb attack on a church in Alexandria, an intervention that was perceived as meddling in Egypt's internal affairs.

Relations have steadily improved since Francis became pope in 2013 with inter-faith dialogue near the top of his agenda, something he underlined with a personal message to the Muslim world to mark the end of the first month of Ramadan of his pontificate.

A representative of the Al-Azhar mosque, Mahmoud Azab, took part in an inter-faith conference at the Vatican in March 2014 aimed at fostering cooperation on combating modern slavery and people trafficking.

"The dialogue was never cut, it was just suspended," Azab said at the time, adding that the idea was not "dialogue for its own sake. There has to be a clear agenda."