Pope Francis knelt and kissed the feet of South Sudan's rival leaders on Thursday, in an act of humility to encourage them to strengthen the country's faltering peace process. At the close of a two-day retreat in the Vatican for the African leaders, the Pope asked South Sudan's president and opposition leader to proceed with the peace agreement despite growing difficulties. He then got down on his knees and kissed their feet. The Pope usually holds a ritual washing of the feet with prisoners on Holy Thursday, but he has never performed such a show of deference to political leaders. "I express my heartfelt hope that hostilities will finally cease, that the armistice will be respected, that political and ethnic divisions will be surmounted, and that there will be a lasting peace for the common good of all those citizens who dream of beginning to build the nation," he said. The spiritual retreat brought together President Salva Kiir and opposition leader Riek Machar. Also present were Mr Kiir's three vice presidents. The Pope also kissed their feet. The South Sudanese leaders did not make any statement in response to the pope's plea for peace. South Sudan gained independence from Sudan in 2011 and in 2013 the country plunged into a civil war in which at least 400,000 people died. The Vatican meeting was held a month before the end of the shaky peace deal's pre-transitional period. On May 12th, Mr Machar is expected to return to South Sudan and again serve as Mr Kiir's deputy. But the agreement, which was signed in September in Khartoum, the capital of Sudan, has been delayed by missed deadlines and continued fighting, with major parts still not implemented.