Pope Francis and Morocco's King Mohammed VI called on Saturday for the protection of Jerusalem's multi-religious character, saying the city's sacred sites must be accessible to worshippers of all faiths.

In a joint appeal signed on the first day of Francis' visit to Rabat, the pope and the monarch said they were "deeply concerned for its spiritual significance and its special vocation as a city of peace".

Since U.S. President Donald Trump announced Washington's decision to move the U.S. embassy to Jerusalem in 2017, the pope, other Christian leaders and Muslim heads of state have stepped up their expressions of concern for the city.

"We consider it important to preserve the Holy City of Jerusalem / Al-Quds Acharif as the common patrimony of humanity and especially for the followers of the three monotheistic religions, as a place of encounter and as a symbol of peaceful coexistence, where mutual respect and dialogue can be cultivated," said the joint appeal, using the Arab name for Jerusalem.

It called for "full freedom of access" for Jews, Muslims and Christians and a guarantee of their right to worship there.

The Vatican backs a two-state solution to the Palestinian-Israeli conflict, with both sides agreeing on the status of Jerusalem as part of the peace process.

Palestinians want East Jerusalem as the capital of their future independent state, whereas Israel has declared the whole city to be its "united and eternal" capital.

Speaking several days after Trump announced the move in 2017, the pope called for the city's "status quo" to be respected, saying new tensions in the Middle East would further inflame world conflicts.

The Moroccan and Jordanian kings signed a similar joint statement on Thursday.