I have spoken at some length to the question that must weigh on our minds and our hearts as we choose to wage war. But let me now turn to our effort to avoid such tragic choices, and speak of three ways that we can build a just and lasting peace.

First, in dealing with those nations that break rules and laws, I believe that we must develop alternatives to violence that are tough enough to actually change behavior -- for if we want a lasting peace, then the words of the international community must mean something. Those regimes that break the rules must be held accountable. Sanctions must exact a real price. Intransigence must be met with increased pressure -- and such pressure exists only when the world stands together as one.

One urgent example is the effort to prevent the spread of nuclear weapons, and to seek a world without them. In the middle of the last century, nations agreed to be bound by a treaty whose bargain is clear: All will have access to peaceful nuclear power; those without nuclear weapons will forsake them; and those with nuclear weapons will work towards disarmament. I am committed to upholding this treaty. It is a centerpiece of my foreign policy. And I'm working with President Medvedev to reduce America and Russia's nuclear stockpiles.

But it is also incumbent upon all of us to insist that nations like Iran and North Korea do not game the system. 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. Those who seek peace cannot stand idly by as nations arm themselves for nuclear war.

The same principle applies to those who violate international laws by brutalizing their own people. When there is genocide in Darfur, systematic rape in Congo, repression in Burma -- there must be consequences. Yes, there will be engagement; yes, there will be diplomacy -- but there must be consequences when those things fail. And the closer we stand together, the less likely we will be faced with the choice between armed intervention and complicity in oppression.

This brings me to a second point -- the nature of the peace that we seek. For peace is not merely the absence of visible conflict. Only a just peace based on the inherent rights and dignity of every individual can truly be lasting.

It was this insight that drove drafters of the Universal Declaration of Human Rights after the Second World War. In the wake of devastation, they recognized that if human rights are not protected, peace is a hollow promise.

And yet too often, these words are ignored. For some countries, the failure to uphold human rights is excused by the false suggestion that these are somehow Western principles, foreign to local cultures or stages of a nation's development. And within America, there has long been a tension between those who describe themselves as realists or idealists -- a tension that suggests a stark choice between the narrow pursuit of interests or an endless campaign to impose our values around the world.

I reject these choices. I believe that peace is unstable where citizens are denied the right to speak freely or worship as they please; choose their own leaders or assemble without fear. Pent-up grievances fester, and the suppression of tribal and religious identity can lead to violence. We also know that the opposite is true. Only when Europe became free did it finally find peace. America has never fought a war against a democracy, and our closest friends are governments that protect the rights of their citizens. No matter how callously defined, neither America's interests -- nor the world's -- are served by the denial of human aspirations.

So even as we respect the unique culture and traditions of different countries, America will always be a voice for those aspirations that are universal. We will bear witness to the quiet dignity of reformers like Aung Sang Suu Kyi; to the bravery of Zimbabweans who cast their ballots in the face of beatings; to the hundreds of thousands who have marched silently through the streets of Iran. It is telling that the leaders of these governments fear the aspirations of their own people more than the power of any other nation. And 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.

Let me also say this: The promotion of human rights cannot be about exhortation alone. At times, it must be coupled with painstaking diplomacy. I know that engagement with repressive regimes lacks the satisfying purity of indignation. But I also know that sanctions without outreach -- condemnation without discussion -- can carry forward only a crippling status quo. No repressive regime can move down a new path unless it has the choice of an open door.

In light of the Cultural Revolution's horrors, Nixon's meeting with Mao appeared inexcusable -- and yet it surely helped set China on a path where millions of its citizens have been lifted from poverty and connected to open societies. Pope John Paul's engagement with Poland created space not just for the Catholic Church, but for labor leaders like Lech Walesa. Ronald Reagan's efforts on arms control and embrace of perestroika not only improved relations with the Soviet Union, but empowered dissidents throughout Eastern Europe. There's no simple formula here. But we must try as best we can to balance isolation and engagement, pressure and incentives, so that human rights and dignity are advanced over time.

Third, a just peace includes not only civil and political rights -- it must encompass economic security and opportunity. For true peace is not just freedom from fear, but freedom from want.

It is undoubtedly true that development rarely takes root without security; it is also true that security does not exist where human beings do not have access to enough food, or clean water, or the medicine and shelter they need to survive. It does not exist where children can't aspire to a decent education or a job that supports a family. The absence of hope can rot a society from within.

And that's why helping farmers feed their own people -- or nations educate their children and care for the sick -- is not mere charity. It's also why the world must come together to confront climate change. There is little scientific dispute that if we do nothing, we will face more drought, more famine, more mass displacement -- all of which will fuel more conflict for decades. For this reason, it is not merely scientists and environmental activists who call for swift and forceful action -- it's military leaders in my own country and others who understand our common security hangs in the balance.

Agreements among nations. Strong institutions. Support for human rights. Investments in development. All these are vital ingredients in bringing about the evolution that President Kennedy spoke about. And yet, I do not believe that we will have the will, the determination, the staying power, to complete this work without something more -- and that's the continued expansion of our moral imagination; an insistence that there's something irreducible that we all share.