Financial Times | Katrina Manson:�Donald Trump has touted his summit with North Korean dictator Kim Jong Un as so great a breakthrough that Pyongyang is no longer a nuclear threat to the US.

But he still deems Iran, which is not thought to have nuclear weapons, �a regime of great terror� that does pose a threat to the US. Last month, he tore up a multi-party nuclear agreement that limited Tehran�s nuclear enrichment and took years to negotiate, claiming it was �disastrous� and one-sided. But just how different are the Trump administration�s approaches towards both countries, and what are their chances of success?

How different are the threats from North Korea and Iran?

Experts stress the nuclear threat from North Korea is more serious than that from Iran, because Pyongyang has developed a nuclear arsenal and a means of delivery that can potentially put the US at risk. Mr Trump claimed on Wednesday there was no longer a nuclear threat from North Korea, but scientists estimate the reclusive country has dozens of nuclear warheads and long-range ballistic missiles that could theoretically reach US soil, and much of the programme is shrouded in secrecy.

Iran, by contrast, is not thought to have developed nuclear weapons, has capped its enrichment facilities and has ballistic missiles with a maximum range of 2,000km. It has no known plans to develop an intercontinental ballistic missile to target the US and accepts international inspections.

While Iran has many enemies in the region with no effective allies, North Korea has relations with China, and neighbouring South Korea is keen to forge a lasting peace after decades of tension since the 1950-53 Korean war. How different are the approaches?� Mr Trump prides himself on his ability to pull off big deals and his administration appears to be reaching for demanding solutions to a range of thorny foreign policy problems.

But Jon Wolfsthal, former senior director of arms control and non-proliferation at the National Security Council during the Obama administration, said Mr Trump was treating the pair differently. �Iran would be thrilled to sign up to the exact same deal that North Korea apparently accepted from Trump in Singapore, but it�s not being offered,� he said.

Tom Countryman, former head of non-proliferation at the US state department, said that Mr Trump was asking for things from Iran � such as Tehran giving up its ballistic missiles and making changes in its human rights records and regional policy � that it had not demanded of North Korea. �There�s no consistency,� he said.

Supporters also perceive a wider effort to turn Pyongyang from foe to friend.��Iran was always going to be a bad guy, it was never going to be a US ally [even with the 2015 nuclear deal], but the aim with North Korea is much bigger: to go from bad guy to good guy,� said a person familiar with the summit preparations of both sides.

Does Mr Trump want a more comprehensive deal with North Korea than the one he tore up with Iran?

Yes, and that is a tougher prospect. �If it works, this is going to be something far more robust, far stronger than the Iran deal,� said the same person, adding that the summit was best viewed as�a step towards detailed negotiations by specialists with top-down support.

Alexandra Bell, a former arms control official at the state department, stressed that nothing this complicated had been tried before. �We�ve never convinced a country with nuclear weapons to give them up,� she said. �What we�re attempting to do with the North Koreans will be the most complicated nuclear agreement ever negotiated and would make the Iran deal look like a cakewalk.�

Is Mr Trump offering more concessions to North Korea than to Iran?

Yes, but experts say it might be worth it. �Iran is still at a lower level of threat so the US can try to use its might to dictate terms (although I don�t believe it will work), but any progress on North Korea is progress because the threat is so much greater,� said Mr Wolfsthal, now director of the Nuclear Crisis Group.

The person familiar with negotiation preparations said Mr Trump�s decision to cancel US-South Korea war games � a move that disquieted Congress and critics � was a sensible concession and stopped short of big giveaways. �The president was giving Kim enough face to go back to North Korea, it was a smart move � he gave nothing on the important substantive issue of sanctions but gave Kim a chance to look good,� said the person, adding that Mr Kim faced pressure at home from military and party elites who support the country�s traditionally anti-American position.

Would verification and inspection regimes differ?

The Trump administration has cast doubt on whether the International Atomic Energy Agency, a UN body, has conducted sufficiently stringent inspections in Iran, despite having the world�s most intrusive programme. The North Korea summit declaration made no reference of �verification� but Mr Trump insisted it would be part of any eventual deal.

Experts say verifying North Korea�s capabilities will be harder because, unlike Iran, it has not allowed international inspectors into the country for nearly a decade and much of its programme was hidden. �We had a very good view of what the Iranians had in their possession, how much material they had produced, even before the deal, but North Korea is so much more opaque,� said Michael Elleman, a former weapons inspector and ballistic missile expert.

Dismantling North Korea�s nuclear programme, he added, would take far longer than the Iran deal: �I think 10 years is probably quick as one could do for the entire job.� But Mike Pompeo, US secretary of state, said the administration wanted to see �major disarmament� within Mr Trump�s first term in office.

Iranians burn the American flag outside the former US embassy in Tehran on Wednesday � Bloomberg Are there other reasons why Mr Trump is treating the pair so differently?

While some argued that North Korea needed handling with kid gloves because the threat was more serious, others suggested that Mr Trump saw the geopolitics in a fundamentally different way, and nursed natural hostility towards Iran. �For a variety of reasons the Trump White House has decided that Israel, Saudi Arabia and the United Arab Emirates are more important friends of the US than our allies in Europe or Asia, and those countries are not interested in a diplomatic deal with Iran,� said Mr Countryman.

He argued that Mr Trump also simply cannot bear to support anything initiated by his predecessor, and believes that the Obama administration did not try as hard with North Korea because it was focused on securing success with Iran. There was also the magnetising appeal of the new:��He wants to be seen as solving a problem that other people couldn�t solve,� said Mr Wolfsthal.

Mr Countryman said Mr Trump might yet manage to pull off a remarkable deal with Pyongyang.��There are dozens of reasons to be sceptical, but it is feasible,� he said.��He can get away with meeting dictatorial leaders when others could not.�