“In the final analysis, the acid test of a genuine will to peace is the willingness of disputing parties to expose their differences to the peaceful processes of the United Nations and to the bar of international public opinion which the United Nations reflects. It is only in this way that truth, reason, and justice may come”

1990s, Inaugural celebration address (1994)
Context: We are both humbled and elevated by the honour and privilege that you, the people of South Africa, have bestowed on us, as the first President of a united, democratic, non-racial and non-sexist government.
We understand it still that there is no easy road to freedom
We know it well that none of us acting alone can achieve success.
We must therefore act together as a united people, for national reconciliation, for nation building, for the birth of a new world.
Let there be justice for all.
Let there be peace for all.

An American Peace Policy (1925)

Message delivered to Dey Omar Agha, by Isaac Chauncey and William Shaler , summarizing the Treaty with Algiers (1815) http://avalon.law.yale.edu/19th_century/bar1815t.asp, and U.S attitudes and actions in the Barbary Wars, in refusing to pay ransom or tribute to pirates of the Barbary States, as quoted in History and Present Condition of Tripoli: With Some Accounts of the Other Barbary States http://books.google.com/books?id=YMwRAAAAYAAJ&pg=PA46 (1835) by Robert Greenhow, p. 46<!-- published by T. W. White -->
A paraphrased variant of this seems to have arisen on the internet around 2007: It is … a settled policy of America, that as peace is better than war, war is better than tribute. The United States, while they wish for war with no nation, will buy peace with none.
1810s
Context: The United States while they wish for war with no nation, will buy peace with none, it being a principle incorporated into the settled policy of America, that as peace is better than war, so war is better than tribute.

Kennedy's "focus on a more practical, more attainable peace, based not on a sudden revolution in human nature but on a gradual evolution of human institutions." was quoted by Barack Obama in his Nobel Prize acceptance speech.
1963, American University speech
Context: I am not referring to the absolute, infinite concept of peace and good will of which some fantasies and fanatics dream. I do not deny the value of hopes and dreams but we merely invite discouragement and incredulity by making that our only and immediate goal. Let us focus instead on a more practical, more attainable peace — based not on a sudden revolution in human nature but on a gradual evolution in human institutions — on a series of concrete actions and effective agreements which are in the interest of all concerned. There is no single, simple key to this peace — no grand or magic formula to be adopted by one or two powers. Genuine peace must be the product of many nations, the sum of many acts. It must be dynamic, not static, changing to meet the challenge of each new generation. For peace is a process — a way of solving problems.

Reasoned Proposal to the Central Committee of the League for Peace and Freedom (1867)

No More Vietnams (1987)
1980s

Address to Congress (1945)
Context: If wars in the future are to be prevented the nations must be united in their determination to keep the peace under law.
Nothing is more essential to the future peace of the world than continued cooperation of the nations which had to muster the force necessary to defeat the conspiracy of the Axis powers to dominate the world.
While these great states have a special responsibility to enforce the peace, their responsibility is based upon the obligations resting upon all states, large and small, not to use force in international relations except in the defense of law. The responsibility of the great states is to serve and not to dominate the world.

As quoted in The New York Times (14 August 1964)

1970s, Remarks on Being Reelected (1972)