The need for an international peacekeeping organization after wwII resulted in the development of what organization?

After WWII the winning nations got together and formed the United Nations. Not long after this, the development of the North Atlantic Treaty Organization (NATO) was also developed. This organization has a more focus on wartime and conflict. Due to the question directing towards "peacekeeping" I would say it would be NATO. But the UN would technically also be correct due to it trying to keep peace through cooperation between nations.