"I would speak to him, I would have no problem speaking to him," the businessman said of Kim Jong-un.

Such a meeting would mark a significant change of US policy towards the politically isolated regime.

Democratic front-runner Hillary Clinton decried Mr Trump's "bizarre fascination with foreign strongmen".

The statement, delivered by one of her aides, added that Mr Trump's foreign policy "made no sense".

In a separate development, the BBC has learned that Mr Trump could visit the UK before the presidential election in November.

Diplomats expect his visit to the UK could happen after he formally becomes the Republican party candidate at a convention in July.

Earlier this week Mr Trump said "it looks like we're not going to have a very good relationship" with the UK.

British Prime Minister David Cameron and new London Mayor Sadiq Khan have harshly criticised Mr Trump's proposed ban on Muslims coming to the US.

Mr Trump's comments about North Korea emerged in an interview with Reuters news agency on Tuesday, in which he also expressed disapproval of Russian President Vladimir Putin's military actions in eastern Ukraine.

Mr Putin is a figure who Mr Trump has previously said he respects.

On the subject of North Korea, the New York property developer said he would pursue face-to-face talks and added that he would also put pressure on China, as North Korea's only major ally.

Image copyright Reuters

Image caption North Korea does not have formal ties to many governments around the world

Image copyright Reuters

Image caption Whitehall diplomats may welcome Mr Trump before the November election

North Korea first tested nuclear weapons in 2006, in breach of international agreements, and has made repeated threats of nuclear strikes against South Korea and the US.

Currently, any contact between with the US happens between officials, not at a presidential level.

In the Reuters interview, Mr Trump also called for a renegotiation of the Paris climate agreement, in which more than 170 countries pledged to reduce carbon emissions.

And he said he would dismantle most of the Dodd-Frank financial regulations if he was elected president.

On Tuesday he released financial records claiming he holds $10 billion (£6.9 billion) in assets, although he has so far resisted calls from Democrats to release his full tax returns.

He was also reunited with his old adversary, Fox News presenter Megyn Kelly, with whom he has had a months-long feud.

In a Fox interview, she challenged Mr Trump for repeatedly calling her a bimbo. He did not apologise directly but said: "Excuse me."