Korea hopes fade

President Donald Trump's withdrawal from the Iran nuclear deal is a major setback to US negotiating credibility and will complicate efforts to reach an agreement with Pyongyang over its own more advanced weapons programme, analysts say.

Trump is set to hold a much-anticipated and unprecedented summit with North Korean leader Kim Jong Un in the coming weeks to negotiate over Pyongyang's arsenal, after it last year carried out by far its most powerful nuclear test to date and launched missiles capable of reaching the US mainland.

But the US president Tuesday pulled Washington out of the 2015 accord with Teheran, pouring scorn on the "disastrous" agreement and describing it an "embarrassment" to the United States -- although European signatories and the IAEA say Iran has complied with its obligations.

Antony Blinken, who was deputy secretary of state under Barack Obama, said the White House move "makes getting to yes with North Korea that much more challenging".

"Why would Kim ... believe any commitments President Trump makes when he arbitrarily tears up an agreement with which the other party is complying?" he asked on Twitter.

MIT political science professor Vipin Narang added: "Today is a stark reminder across the world: Deals are reversible and can have expiration dates, while nuclear weapons can offer lifetime insurance."

North Korea remains technically at war after the 1950-53 Korean War ended with a ceasefire rather than an armistice, and Pyongyang has long insisted that it needs nuclear weapons to defend itself from a possible US invasion.

Two weeks ago Trump's new national security advisor John Bolton said "We have very much in mind the Libya model," for the denuclearisation of North Korea.

Libyan leader Muammar Gaddafi agreed to abandon his pursuit of nuclear weapons in the early 2000s, but his government was later overthrown by rebel forces supported by Western air strikes, and he was killed.

Pyongyang regularly cites the fates of Gaddafi and Saddam Hussein in Iraq -- whose government was overthrown in a US-led invasion -- as evidence of the need for nuclear arms.

Former CIA director John Brennan said Trump's "madness" had "undermined global confidence in US commitments, alienated our closest allies, strengthened Iranian hawks, & gave North Korea more reason to keep its nukes".

Analysts pointed to Kim's repeated trips to China as evidence Pyongyang was looking for support from its longstanding diplomatic protector and provider of trade and aid.