Muslims in Iraq should celebrate Ramadan by "renouncing sectarianism and fundamentalism", the Chaldean Catholic Patriarch Louis Sako of Baghdad has said.

Patriarch Sako wrote an open letter to Iraqi Muslims, addressing them as sisters and brothers and urging them to "make this month an 'exceptional Ramadan'".

He asked them to focus on "building a culture of reconciliation" and "promoting shared values of tolerance, neighborhood and friendship".

Large areas of Iraq's western and northern regions have been controlled by ISIS since August 2014, which has displaced millions of people. Thousands have been killed or wounded.

Sako urged Iraqi Muslims to respond to this destruction by promoting "peaceful coexistence, dialogue and mutual respect" between the various communities within the country.

The Chaldean Church will also be praying during the month in solidarity with Iraqi Muslims and the desire for God's protection over Iraq and Iraqis, he said.

He added that he would be praying for God to "enlighten the hearts of all Iraqis toward the birth of a new Iraq, in which all its' citizens will be treated equally, safeguard their dignity and bring them security and stability".

"The month of Ramadan provides a privilege time for fasting, praying, repent (sic) and changing of mentality and approaches in order to live in peace with oneself and with others," he wrote.