An Christmas Day appeal for peace addressed to leaders in South Sudan has been issued by Pope Francis, the head of the Roman Catholic Church and Anglican Archbishop Justin Welby of Canterbury, leader of the Anglican Communion, joined by the Rev. John Chalmers, former moderator of the Church of Scotland.

"In this Christmas season and at the beginning of a new year, we wish to extend to you and to all the people of South Sudan our best wishes for your peace and prosperity, and to assure you of our spiritual closeness as you strive for a swift implementation of the Peace Agreements," the leaders said.

"We raise our prayers to Christ the Saviour for a renewed commitment to the path of reconciliation and fraternity, and we invoke abundant blessings upon each of you and upon the entire nation. May the Lord Jesus, Prince of Peace, enlighten you and guide your steps in the way of goodness and truth, and bring to fulfilment our desire to visit your beloved country."

During a meeting at the Vatican in November, the Pope and Archbishop agreed to travel together to South Sudan if the country's leaders implement their pledge to form a transitional government by late February. South Sudan President Salva Kiir and former Vice President Riek Machar missed two deadlines for forming a unity government originally set to take place in May and then November. The end of February is the latest target date agreed by the two leaders.