President Trump again denounced the Iran nuclear deal Tuesday, calling it a “terrible deal” and adding: “It’s insane, it’s ridiculous. It should have never been made.” This obviously has implications for whether the U.S. pulls out of the agreement with Iran – but also could kill any chance for substantive talks with North Korea on denuclearization before they even begin.

President Trump and French President Emmanuel Macron later called for a new nuclear deal with Iran during a joint news conference at the White House. President Trump has a May 12 deadline to decide if the U.S. should remain part of the current Iran deal.

What does an agreement with Iran have to do with an agreement with North Korea? If North Korean dictator Kim Jong Un sees that President Trump can’t be trusted to keep a nuclear deal with Iran, Kim could reasonably conclude that Trump can’t be trusted to honor a possible nuclear agreement with North Korea.

President Trump and Kim are planning to meet in late May or June. And Kim is scheduled to meet with South Korean President Moon Jae-in on Friday.

The Iran deal is an agreement between Iran, the U.S., the European Union, and five other world powers that suspended tough international economic sanctions on Iran in return for restrictions on Iran’s nuclear program.

The deal was reached by the Obama administration and other nations in 2015 after many nations concluded that Iran was close to developing fissile material that could be used to build nuclear weapons.

At first blush, taking a hard line on Iran might seem like a good way to show the North Koreans that President Trump means business. But if Trump backs out of the nuclear agreement – without any evidence that Iran is cheating – that could easily lead Kim to believe Trump would do the same thing to North Korea.

Even under the best-case scenario, there is only the slimmest chance that Kim would be willing to negotiate away his prized nuclear program. He’s well aware that giving up a nuclear program – as Libya and Ukraine did – or failing to develop nuclear weapons, as was the case with Iraq, can leave a country more vulnerable to attack or even “regime change.”

As North Korea’s state-controlled media exclaimed after one nuclear test: "The Saddam Hussein regime in Iraq and the Gaddafi regime in Libya could not escape the fate of destruction after being deprived of their foundations for nuclear development and giving up nuclear programs of their own accord."

Iran offers a powerful counter-example – for now. The promise of the historic agreement between Iran and the world’s major powers was that in exchange for giving up its nuclear ambitions, a rogue regime could re-engage with the international community, earn relief from crippling sanctions and boost its economy.

Iran had to take a leap of faith to accept that deal. It ended its plutonium program, curtailed its uranium enrichment program, and agreed to render key parts of nuclear cycle inoperable – all before it received any sanctions relief.

Iran acceded to unheard of intrusive inspections, including round-the-clock access to every nuclear site, continuous monitoring of its nuclear facilities via cameras and other means, and the ability for inspectors to gain access to undeclared sites, including military ones.

The Iranians agreed to do all this because they trusted the international community – and especially the United States – to uphold the other end of the bargain.

If now – after dismantling its nuclear program – Iran doesn’t get the benefits it was promised, America’s word will no longer carry any weight. That will teach leaders like Kim to never make the same mistake Iran did and never make a deal with the United States.

Kim might still go through the theater of sitting down with President Trump, because the North Koreans crave the prestige and legitimacy such a meeting would convey. But Kim won’t seriously consider giving up the protection his nuclear program provides for a deal President Trump could easily tear up whenever it suits him.

Even now, President Trump’s belligerence towards Iran is weakening his negotiating hand with North Korea. In the unlikely scenario that Kim wants to negotiate seriously, the only deal President Trump could now reasonably hope for would be more limited and therefore less likely to succeed than the comprehensive deal with Iran.

This may sound counterintuitive, given how much criticism we’ve heard about the Iranian agreement. But President Trump may end up wishing he could get something even half as strict or sweeping as the deal President Obama negotiated with Iran.

Kim won’t let himself be subjected to the uncertainty Iran is now facing – no future foreign government will.

So Kim seems certain to demand more assurances from President Trump and offer fewer concessions. In any negotiation where there is a total lack of trust, it’s common for governments pursue an incremental approach rather than trying for anything sweeping.

The idea is for both parties to take small steps to build confidence before attempting anything bigger. This is what the Clinton administration did with North Korea in 1994 when it signed the Agreed Framework, an incremental deal to freeze and dismantle two North Korean nuclear reactors.

The Agreed Framework ultimately failed. One of the lessons the Obama administration took away from that failure was the need to avoid half measures and pursue a more comprehensive agreement with Iran – one that covered the entire nuclear fuel cycle, not just a few reactors. President Trump likely won’t have that option.

As a result, President Trump’s threats to tear up the Iran deal are weakening his negotiation position with Kim before even sitting down at the table.

President Trump would do well to take the opposite approach and strengthen his hand by sending North Korea a message that these kinds of deals can in fact work. The only way to do that is to stay in the Iran nuclear agreement.