Which U.S. president said, "Let us never negotiate out of fear, but let us never fear to negotiate"?

The overarching principle, elegantly expressed, by John F. Kennedy was this: “Let us never negotiate out of fear. But let us never fear to negotiate.” President Kennedy was speaking directly about situations where negotiations will take place and the attitude and approach that ought best be taken if success is to be achieved.

On January 20, 1961 in Kennedy's inauguration speech, he stressed that negotiation must come from a position of strength. He said, “We dare not tempt them with weakness” – an important point, but it was not the most important one from this speech. For he went on to say, “to those nations who would make themselves our adversary,” the United States offers “not a pledge but a request: that both sides begin anew the quest for peace.”

At that time, he was speaking about needs of the U.S. and the Soviet Union. There was not only a clear need to negotiate, but there was also the key question of what any negotiations should actually be about: “Let both sides explore what problems unite us instead of belaboring those problems which divide us."

So, President Kennedy then actually presented a set of universal principles, or precepts, appropriate to most deadly serious situations, which parties could use in conducting negotiations.