An agreement to end Latin America's last armed conflict is the start of a process of positive change for Colombia, Cardinal Pietro Parolin said hours before the government and Marxist rebels were set to sign peace accords on September 26.

"This country of Catholics has come together in prayer," the Vatican secretary of state said before roughly 2,500 who had gathered in St Peter Claver Church in Cartagena. "Colombians have lived through forced displacements and violence. ... And that is why we need to find the road to peace and justice."