Mr. Trump’s aides see the problem and in an entirely different way.
The lesson that the North Koreans would take away from the Iran deal, they say, is that the United States can be rolled. The Iran deal is not a permanent solution to the Iranian nuclear problem, they argue, but just a temporary fix. After 15 years, many of the limits on the production of nuclear material will be lifted, even if inspection requirements remain.
“If we’re going to stick with the Iran deal there has to be changes made to it,” Secretary of State Rex W. Tillerson said on Fox News on Tuesday. “The sunset provisions simply is not a sensible way forward,” he added, arguing that they amount to “kicking the can down the road.”
Mr. Trump’s argument goes further. In interviews with The New York Times last year, he criticized the deal as failing to address Iran’s missile capability, the detention of American citizens and Tehran’s support of terrorist groups around the Middle East. He seeks something more akin to a “grand bargain” with Iran, something the nuclear deal was never intended to be.
Mr. Tillerson will have an opportunity to make these arguments on Wednesday at a meeting of all the signatories of the Iran deal, including his Iranian counterpart, Foreign Minister Mohammad Javad Zarif. Mr. Zarif used to talk or email every few days with John Kerry, the American secretary of state who negotiated the deal.
In an interview this summer, Mr. Zarif said he and Mr. Tillerson had never spoken, and the American-educated Iranian diplomat left little doubt on Tuesday what he thought of Mr. Trump’s address to the United Nations General Assembly, in which the president called the Iranian leadership a “corrupt dictatorship” that masks itself as a democracy.
“Trump’s ignorant hate speech belongs in medieval times — not the 21st Century UN — unworthy of a reply,” Mr. Zarif tweeted. (While they will be in the same room, it is not clear if Mr. Zarif and Mr. Tillerson will talk directly.)
In the end, this entire argument may be moot. China and Russia have said they have no interest in renegotiating the deal. Britain and France have said they would be willing to engage Iran in a negotiation over an addendum to the accord, but the Iranians have rejected that out of hand. And the White House has never said what, if anything, it was willing to give up in return for renegotiating the terms.
What is missing from this debate is obvious: If Mr. Tillerson extracted anything resembling the Iran agreement from North Korea, it would mark a historic breakthrough, one any of the four previous American presidents would rightly have celebrated.
The accord that Mr. Trump finds so lacking would prevent Iran from assembling the makings of a bomb for a year or so, by the best estimates of American national nuclear laboratories, which advised the negotiators. By comparison, North Korea already has an arsenal of 20 to 60 fully formed weapons, depending on whose intelligence estimates one believes.
In the best case scenario, some administration officials say, the Trump administration would be lucky to win a nuclear “freeze” that keeps North Korea from conducting more nuclear and missile tests.
But that would enshrine the North Korean nuclear arsenal at something around its current level, an outcome Mr. Trump and his national security adviser, H.R. McMaster, have already rejected as intolerable. And it is possible that the North is even more capable than we know, some experts say.
Michael J. Morell, a former deputy director of the C.I.A., recently argued that the North most likely already had everything it needed to mount an attack on the mainland United States – and that the only solution is classic containment.
“I believe that North Korea may have the capability today to successfully conduct a nuclear attack on the United States,” he wrote recently, saying that Washington was relying on flawed logic in its assumption that Pyongyang did not possess the technology needed to deliver a warhead to Los Angeles or Chicago simply because it had yet to demonstrate the mastery of those technologies.
If Mr. Morell is right — and no one will know until the North Korean regime collapses and inspectors can assess the extent of its technology — Mr. Trump faces a problem far more urgent than the one that confronted President Barack Obama in Iran.
Over the next few months, Mr. Trump must decide whether it is truly worth the many risks of war to force the North to disarm, as he has seemed to suggest several times, including in his United Nations speech, or whether he can acquiesce to Cold War-style containment.
So while Mr. Tillerson presses the Europeans to add restrictions on Iran, Mr. Trump and the Treasury secretary, Steven Mnuchin, will be focusing on pressuring China to cut off Pyongyang’s supplies of oil and gas.
Mr. Mnuchin says he has already drawn up a list of potential sanctions on Chinese banks, barring those that deal with North Korea from also dealing with the United States. (It is less likely that Mr. Trump will make good on his tweeted threat to cut off all trade with any country that does business with North Korea, which would exact a huge cost on the American economy.)
But few expect that pressure campaign to work, and there is already discussion of Plan B. Most of those scenarios are in the category of what Daniel Russel, the former assistant secretary of state for Asia, described to the news site Axios as “a sharp, short ‘warning shot’” that could change Mr. Kim’s calculus about the American willingness to use force.
It is not clear what a warning shot might look like. Inside the Pentagon, military officials say they are looking at several options, including cyber attacks that could turn off Pyongyang’s lights and shooting down North Korean test launches — though Defense Secretary Jim Mattis noted on Monday that the United States had avoided doing so as long as the missiles looked as though they would fall harmlessly into the sea.
Mr. Mattis, who previously said a war with North Korea would be “tragic on an unbelievable scale,” now says he is confident that there are military approaches that do not risk retaliation against Seoul. The South Korean capital is 35 miles from of the Demilitarized Zone that separates the two countries, well within range of thousands of pieces of North Korean artillery.
Reporters asked how that might be possible. New technology? A way of finding and silencing North Korea’s mortars?
“I won’t go into detail,” Mr. Mattis said.
In an earlier version of this article, a picture caption referred incorrectly to the North Korean ambassador shown during a session of the General Assembly. The ambassador, Ja Song-nam, was pictured before — not during — President Trump’s speech.