The U.S. says the 'ball is now in Russia's court.' But what really happens if Putin agrees to a ceasefire?

Ukraine agreeing to an interim ceasefire along the sprawling 1,200 kilometre frontline Tuesday was hailed as a major step toward peace, but Russia has yet to respond to the U.S. proposal and reaching an agreement will be a challenge, observers say. If Russia does accept, making the truce an enduring one could involve thousands of peacekeepers.