On Wednesday, President Obama will urge Americans — and Congress — to support an agreement that would limit Iran’s nuclear weapons program despite an atmosphere of mistrust. (Susan Walsh/AP)

An eloquent young president, elected with only brief experience in the Senate, is facing a nuclear weapons threat abroad and a chorus of criticism at home. So he chooses to make the short trip to American University to give a speech urging Americans to take a chance for peace and explore a weapons agreement with a country no one trusts.

In it, he calls for a “practical, more attainable peace” that is “the necessary rational end of rational men.”

The president was John F. Kennedy, the year was 1963, and his purpose was to reach a nuclear test-ban treaty with the Soviet Union just eight months after the Cuban missile crisis.

On Wednesday, there will be echoes of that Kennedy moment when President Obama goes to American University to deliver a similar message, urging Americans — and Congress — to support an agreement that would limit Iran’s nuclear weapons program despite an atmosphere of mistrust.

A White House official said Obama would call the vote on the deal “the most consequential foreign policy debate since the decision to go to war in Iraq.” The president will link the two, asserting that “the same people who supported war in Iraq are opposing diplomacy with Iran and that it would be an historic mistake to squander this opportunity.”

“What’s appropriate about that comparison is President Kennedy, more than 50 years ago, entered into a diplomatic agreement with an adversary of the United States that did succeed in advancing the national security interests of the United States,” White House press secretary Josh Earnest said Tuesday.

Obama’s task may be even more difficult than Kennedy’s. On Tuesday, Israeli Prime Minister Benjamin Netanyahu did a webcast for more than 10,000 Jewish Americans in which he said that “this is the time to oppose this dangerous deal.” And Congress is likely to vote against the Iran deal. House GOP leaders said Tuesday that they would vote in September for a formal resolution of disapproval introduced by House Foreign Affairs Committee Chairman Edward R. Royce (R-Calif.).

But Obama hopes that he can protect the Iran agreement by using his veto power and that opponents will not be able to summon enough support to override it. The administration got a big boost Tuesday when three influential and previously undecided Senate Democrats — Barbara Boxer (Calif.), Timothy M. Kaine (Va.) and Bill Nelson (Fla.) — endorsed the agreement.

The president is still working to persuade other undecided Democrats, most notably Sen. Charles E. Schumer (N.Y.).

Boxer, after meeting with senior diplomats from Britain, France and Germany, endorsed the deal, saying that she was “more convinced than ever that a rejection of the Iran nuclear agreement would be a victory for Iranian hard-liners and would accelerate their ability to obtain a nuclear weapon.”

Kaine said the talks with Iran had “shown that patient diplomacy can achieve what isolation and hostility cannot.” Acknowledging compliance risks and the lack of broader change in Iran, Kaine said on the Senate floor that “this deal does not solve all outstanding issues with an adversarial regime. In that sense, it is similar to the nuclear test-ban treaty that President Kennedy negotiated with the Soviet Union in the midst of the Cold War.”

Being compared to Kennedy is rarely a bad thing for Democrats in politics these days. And Obama had a “special affinity” for the late Sen. Edward M. Kennedy, said presidential historian Jeff Shesol, a former speechwriter for President Bill Clinton and a partner at West Wing Writers.

In the June 1963 American University commencement address, Kennedy was at the peak of his rhetorical power. Much as Obama has recently portrayed war as the alternative to the negotiated deal with Iran, Kennedy warned that “too many of us think it [peace] is impossible. Too many think it is unreal. But that is a dangerous, defeatist belief. It leads to the conclusion that war is inevitable.”

Peace, Kennedy said, “does not require that each man love his neighbor. It requires only that they live together with mutual tolerance, submitting their disputes to a just and peaceful settlement.” He added: “Let us not be blind to our differences, but let us also direct attention to our common interests.”

“Kennedy was intensely concerned with finding a way with the Soviet Union over nuclear arms,” said presidential historian Robert Dallek. “The missile crisis frightened him and frightened [Soviet leader Nikita] Khrushchev because they came within hailing distance of nuclear war.”

At the same time, Shesol said, “no one could credibly accuse John Kennedy of being soft on the Soviets or soft on communism. If there’s an analogy to be made, it’s that you negotiate out of strength. And you negotiate to strengthen national security. That clearly is how President Obama sees this agreement with the Iranians.”

Obama could tear a page from Kennedy’s speech without altering a word. Like Obama with Iran, Kennedy did not ask Americans to trust the Soviet Union.

“No treaty, however much it may be to the advantage of all, however tightly it may be worded, can provide absolute security against the risks of deception and evasion,” Kennedy said. “But it can — if it is sufficiently effective in its enforcement and it is sufficiently in the interests of its signers — offer far more security and far fewer risks than an unabated, uncontrolled, unpredictable arms race.”

The White House on Tuesday did not enumerate similarities with Kennedy and the nuclear test-ban treaty, worried about taking on even more baggage than the Iran deal already has.

Earnest said that Kennedy had to make concessions to the Soviet Union in the test-ban treaty that was reached in August 1963, two months after the AU speech. Earnest said that Obama, by contrast, “didn’t have to make any concessions.” He stressed that “there’s no impact from this nuclear agreement on the United States and our — either our nuclear programs or our military programs.”

The president deployed all his arguments in a nearly two-hour meeting Tuesday evening at the White House with two dozen leaders of the American Jewish community and pro-Israel groups, some supporters and others opponents of the plan. People involved in the discussion said Obama was forceful in arguing that the nuclear agreement, while not perfect, is a preferable to alternatives that would be likely to lead to a military confrontation.

Obama, while acknowledging some of the activists’ concerns, expressed frustration at the intensity of the public criticism some of the opponents were mounting, participants said. 

“At one point, he essentially said this would not be as big an issue and as big a fight if basically the pro-Israel community was not making it into a big fight,” said one participant who spoke on the condition of anonymity to discuss a private meeting. “That’s the only reason why we are where we are. So essentially, the takeaway was that he was broadly asking the organizations to consider stepping back.”

Obama pointedly noted that the American Israel Public Affairs Committee (AIPAC) was spending $20 million in an ad campaign to denounce the deal. The activists countered that Obama was unfairly characterizing opponents of the deal as preferring a military confrontation, according to people in the room. 

The president suggested to AIPAC that “if you guys would back down, I would back down from some of the things I’m doing,” said the person involved in the discussion, who added, “I don’t think AIPAC will take him up on it.”

Obama said that if the deal were to fall apart, he would likely face calls within three to six months to use military strikes to stop Iran from obtaining a nuclear weapon. “To the president’s credit, he kept acknowledging the legitimacy of the concerns of the critics,” the person in the room said. “He wasn’t saying that the concerns and criticisms were not warranted. Iran is a terrible actor on one hand; he wasn’t going to the point of saying, ‘You guys are just crazy,’ but he was saying, ‘To suggest there’s a better way to do this is not realistic.’­ ” 

Netanyahu in his webcast took on Obama’s suggestion that rejecting the deal would mean war. “I don’t oppose this deal because I want war, but because I want to prevent war,” Netanyahu said. The time limits of the agreement mean Iran would have an easier time developing a bomb in 10 or 15 years, he said, calling that period “the blink of an eye.” 

Obama’s speech is also a bookend to a more ambitious speech he delivered in Prague in 2009. Then, Obama said the United States would “seek a new treaty that verifiably ends the production of fissile materials intended for use in state nuclear weapons.” But Pakistan, which some experts say will add 20 nuclear weapons to its stockpile this year, has blocked moves to cut off such supplies in international talks that require unanimity.

Obama also vowed to strengthen the nuclear Non-Proliferation Treaty, but the review conference failed to approve a consensus document earlier this year.

The president did win congressional approval for an important new START pact on Christmas Eve 2009, but more recent efforts to engage Russia have fizzled.