The United States aspires to have North Korea as a “close partner” and not an enemy, the US secretary of state has said.

Mike Pompeo noted the US has often in history become good friends with former adversaries.

He said he told North Korean leader Kim Jong Un of that hope during his brief visit to Pyongyang earlier this week, during which he finalised details of the upcoming June 12 summit between Mr Kim and President Donald Trump and secured the release of three Americans imprisoned in the country.

He said talks with Mr Kim on Wednesday had been “warm”, “constructive”, and “good” and he made clear if North Korea gets rid of its nuclear weapons in a permanent and verifiable way, the US is willing to help the impoverished nation boost its economy and living stands to levels like those in prosperous South Korea.

“We had good conversations about the histories of our two nations, the challenges that we have had between us,” Mr Pompeo told reporters at a news conference with South Korea’s visiting foreign minister Kang Kyung-wha.

“We talked about the fact that America has often in history had adversaries who we are now close partners with and our hope that we could achieve the same with respect to North Korea.”

US secretary of state Mike Pompeo, left, with North Korean leader Kim Jong Un on Wednesday (Korean Central <a href=News Agency/Korea News Service/AP)">US secretary of state Mike Pompeo, left, with North Korean leader Kim Jong Un on Wednesday (Korean Central News Agency/Korea News Service/AP)

He did not mention other adversaries by name, but Mr Pompeo and others have often noted the US played a major role in rebuilding Japan and the European axis powers in the wake of the Second World War.

With US help, those countries recovered from the devastation of conflict.

“If North Korea takes bold action to quickly denuclearise, the United States is prepared to work with North Korea to achieve prosperity on the par with our South Korean friends,” he said.

Ms Kang praised the upcoming meeting between Mr Trump and Mr Kim in Singapore as a “historic” opportunity, but added a few notes of skepticism as well.

Amid concerns North Korea will demand the US withdraw its troops from neighboring South Korea, Ms Kang emphasised the US military presence there must be “a matter for the US-ROK alliance first and foremost”, using an acronym for South Korea’s official name, the Republic of Korea.

She said the US troop presence in the South for the past 65 years has played a “crucial role for deterrence”, peace and stability on the Korean peninsula.

South Korean foreign minister Kang Kyung-wha, left, and Mr Pompeo (Alex Brandon/AP)South Korean foreign minister Kang Kyung-wha, left, and Mr Pompeo (Alex Brandon/AP)

Therefore, she added, any change in the size of the US forces in the South Korea should not be on the table at the summit.

“The next few weeks will be critical, requiring air-tight coordination between our two countries,” Ms Kang said, noting South Korean President Moon Jae-in would be in Washington to see Mr Trump later this month.

Since Mr Trump announced plans to hold a summit with Mr Kim, questions have been raised continually about whether the two leaders have the same objective in mind when they speak about “denuclearisation”.

To the US, that means the North giving up the nuclear weapons it has already built. But North Korea has said it is willing to talk now because it has already succeeded in becoming a nuclear-armed state, fueling skepticism the North would truly being willing to give those weapons up.

Mr Pompeo said there would need to be “complete” and “verifiable” denuclearisation that would remove North Korea as a threat to the South, the United States and the rest of the world.

He said a massive inspection and monitoring regime would be required to ensure the North’s compliance.

“I think there is complete agreement about what the ultimate objectives are,” he said, though declined to offer more detail.