Russia and Ukraine swapped hundreds more prisoners on Saturday, as part of a major swap that was a moment of cooperation in otherwise failed efforts to reach a ceasefire.

Russia and Ukraine began a major prisoner exchange Friday, swapping hundreds of soldiers and civilians in the first phase of an exchange that was a moment of cooperation in otherwise failed efforts to reach a ceasefire in the 3-year-old war.

The Vatican has a deep history of conflict mediation, with varying degrees of success. An effort by the pope to end the war in Ukraine would face long odds.