US President Barack Obama chastized those in the international community who turned a blind eye to Iran's nuclear ambitions, during his Nobel Peace Prize acceptance speech Thursday. "Those who claim to respect international law cannot avert their eyes when those laws are flouted. Those who care for their own security cannot ignore the danger of an arms race in the Middle East or East Asia," he declared. "Those who seek peace cannot stand idly by as nations arm themselves for nuclear war." He said that while the US and other nuclear powers must move toward disarmament, "it is also incumbent upon all of us to insist that nations like Iran and North Korea do not game the system." Obama backed the idea of "painstaking diplomacy" - even though "engagement with repressive regimes lacks the satisfying purity of indignation" - as the only way to make punitive measures like sanctions effective. But he stressed that diplomacy wasn't enough: "Yes, there will be engagement; yes, there will be diplomacy - but there must be consequences when those things fail." And in some cases, he made clear, the US wouldn't even extend that prospect. "I face the world as it is, and cannot stand idle in the face of threats to the American people," he explained. "For make no mistake: Evil does exist in the world. A nonviolent movement could not have halted Hitler's armies. Negotiations cannot convince al-Qaida's leaders to lay down their arms." His speech, delivered in Norway, was in part a push-back against those who would criticize any resort to the use of force, a sentiment popular in some parts of Europe. "I understand why war is not popular, but I also know this: The belief that peace is desirable is rarely enough to achieve it," Obama told them. Obama stressed several times the universal importance of human rights and America's role in promoting them, singling out the Iranian demonstrators as important activists needing support, along with those in Burma and Zimbabwe. "It is the responsibility of all free people and free nations to make clear that these movements - these movements of hope and history - they have us on their side," he said. Obama also spoke about some of the trends in history that have provided more discord rather than less, referring to the Israeli-Palestinian conflict and the fear of "the loss of what they cherish in their particular identities - their race, their tribe, and perhaps most powerfully, their religion." The president said that "in some places, this fear has led to conflict. At times, it even feels like we're moving backwards. We see it in the Middle East, as the conflict between Arabs and Jews seems to harden." Still, he finished on a positive note, speaking of the hope that the world would be improved, if not perfect. "Clear-eyed, we can understand that there will be war, and still strive for peace," he said. "We can do that - for that is the story of human progress; that's the hope of all the world; and at this moment of challenge, that must be our work here on Earth."