President Trump boldly announced last week that he would meet with North Korean leader Kim Jong Un to talk disarmament, working to fulfill his recent State of the Union promise to prevent Pyongyang from obtaining nuclear missiles that could hit the U.S. homeland. In making that pledge, Trump declared, “I will not repeat the mistakes of past administrations.”

At the same time, Trump has been relentless in criticizing predecessor Barack Obama not only for failing to defuse the North Korea threat, but also for the nuclear disarmament deal he did succeed in striking — the agreement with Iran. Calling that pact fundamentally flawed and unenforceable, Trump indicated that his standards for non-proliferation agreements are exceptionally high. (He still hasn’t spelled out clearly what “denuclearizing” Pyongyang — the Trump administration’s stated goal — would look like).

The contrast between the Trump administration’s approaches to North Korea and Iran indicates how difficult it will be for the president to fulfill his promise regarding Pyongyang’s nuclear program — Trump so far has put himself in a worse bargaining position with North Korea than Obama was at the start of the Iran talks, and the challenge in North Korea is even greater.

Obama was in a better position with Iran

After several months of secret contacts between U.S. and Iranian officials, Obama signed off on the start of a formal negotiation process in November 2013. He entered those talks with several advantages over Trump’s current situation; in particular, Obama had secured an interim agreement in which Tehran promised to freeze its nuclear progress, meaning that it couldn’t use the talks simply to buy more time as it tried to obtain a nuclear weapon.

Trump has no such commitment. While Kim allegedly offered to halt nuclear and missile tests this week while negotiating with the Americans, he made no pledge to stop the work that precipitated the current crisis: miniaturizing a nuclear warhead and fitting it atop an missile capable of reaching the U.S. mainland. And North Korea has dragged out negotiation processes in the past.

Obama was in a better position with the world

The main reason that Iran came to the negotiating table in 2013 is that the world had unified behind a far-reaching international sanctions campaign targeting Tehran over its nuclear work. Led by the U.S. but brokered through the United Nations, there was near-universal agreement that it was essential that Iran be kept from getting the bomb, even at the price of hurting domestic economies. The result was sanctions that caused Iran real pain.

In addition, five world powers (the other permanent members of the U.N. Security Council — the U.K., France, Russia and China — and Germany) had come together with the U.S. to conduct the negotiations, meaning that Iran couldn’t play countries off one another and any agreement signed had much greater heft.

Though North Korea is under tight international sanctions and has a decimated economy, the biggest economy in the world — and the one country that is a lifeline for Pyongyang — hasn’t ever signed onto the U.S. strategy: China. Trump said during the campaign that his game plan for taking on the North Korean regime would be to enlist Beijing, but while he has made some progress in that direction, there is far from a unified vision between the two powers about how to treat North Korea.

Obama was in a better position with his administration

The U.S. had laid years of groundwork before entering into talks with Iran. Well before Obama took office, the George W. Bush administration started the sanctions regime that ultimately proved critical. Washington had accumulated experience on how best to target sanctions; how to assess Iran’s behavior in talks; and where they were most likely to find common ground.

Obama also had the full support of his Cabinet — necessary for a negotiation that requires the tireless diplomatic efforts of a secretary of state, the scientific expertise of an energy secretary, the sanctions enforcement of a Treasury secretary and the muscle of a defense secretary. Each step of the process was overseen by the entirety of the National Security Council.

Trump, in contrast, reportedly made a snap decision to meet with Kim and didn’t so much as consult with his National Security Council. It was “a decision the president took himself,” Secretary of State Rex Tillerson said plainly on Friday, mere hours after telling journalists traveling with him in Africa that direct negotiations were far down the line. Tillerson — who is nominally leading efforts to engage the North diplomatically — seems to have found out about the summit around the same time as the rest of us.

Then there are the many ways that the North Korea situation is a tougher nuclear nut to crack than Iran’s missile program. That might be part of the reason that it was the top unfinished crisis item that Obama left on Trump’s desk, warning on his way out that it would be the new president’s greatest challenge.

North Korea has a stronger nuclear position than Iran

Iran did not already have nuclear weapons during those 2013-2015 negotiations. But North Korea does. Tehran was still in the process of producing highly enriched uranium usable for nuclear weapons and was only on the threshold of a nuclear weapons capacity when the interim deal froze the program.

Pyongyang already has up to 60 warheads, according to U.S. intelligence community assessments. At this point, the Koreans are simply perfecting their delivery vehicle, an intercontinental ballistic missile capable of reaching any part of the U.S..

Put simply: The more advanced the program, the more embedded it is in a nation’s military and national security strategy, the more spread out its infrastructure is across the country, the more difficult it’s going to be to detect, monitor and dismantle. And on all of these scores, Pyongyang is far beyond where Tehran ever was.

North Korea has a better ability to hide its activities

One of the central pillars of the Iran deal is the requirement for constant monitoring of Tehran’s declared nuclear-related sites and expedited access for inspectors to other sites upon request. This is meant to cover Iran’s entire nuclear fuel cycle — or, in the words of skeptical Western diplomats, the “chain of evidence” of their nuclear activity — from start to finish, including its uranium mines and mills and enrichment and storage facilities. Meanwhile, the North Korean technology in contention — building ICBMs — is a matter of quiet and undetectable military research and development. Kim’s government could be working in laboratories the U.S. never knows about.

Furthermore, the U.N.’s International Atomic Energy Agency is allowed to inspect only areas to which it has either been invited or where a nation has agreed to cede oversight control. Bet world powers would not know where to begin negotiating for access in North Korea, because it has no real grasp on where all the nuclear-related facilities are hidden. In other words, U.S. intelligence has extremely low confidence in where those 60-odd warheads are — if that’s the right number.

In addition, all of North Korea’s nuclear facilities are de facto military facilities — a significant barrier to inspections, as nations of all stripes argue it’s a violation of their sovereignty to grant U.N. monitors access to military sites. The IAEA would be dependent on Pyongyang providing an exhaustive list of nuclear facilities, even though it has consistently lied throughout the lives of past agreements.

Trump started out in a weak position on North Korea and now is poised to enter talks from an even poorer posture. His lack of specificity about the terms of denuclearization means that his negotiators must enter high-stakes talks without knowing his own parameters for success. And then there’s Pyongyang’s wager that U.S. military options would be frozen so long as both parties remain at the negotiating table — raising the risk that North Korea is, once again, buying itself valuable time through talks to advance its nuclear arsenal.

Meanwhile, the president’s hardline position on the Iran deal could affect his negotiating posture with North Korea. At roughly the same time he plans on meeting with Kim, he is threatening to pull out of the Iran accord if the Europeans don’t provide assurances that they are willing to strengthen it — suggesting that the U.S. cannot be trusted to follow through on its promises across governments, among other messages.

Of course, whether Trump decides to go ahead with the summit under these conditions is far from certain. White House officials are already backpedaling on the president’s firm commitment to the South Koreans that he would sit down with Kim by May.