North Korea has threatened to walk away from its summit with President Trump if the US refuses to lift sanctions until after its nukes have been dismantled.

In a blistering statement the hermit state criticized the US and South Korea for holding joint military drills, saying they are preparing for an invasion of the North.

A second statement then attacked 'repugnant' National Security Adviser John Bolton for suggesting that the North would have to give up its weapons first, before being compensated later.

Instead, America will have to end 'hostile policy, nuclear threats and blackmail' as a 'precondition' for denuclearisation, the North said.

Kim Jong Un will walk away from his planned summit with Donald Trump if the US refuses to lift economic sanctions before its nuclear weapons are dismantled, the North Korea regime says

North Korea took particular issue with 'repugnant' National Security adviser John Bolton and accused him of trying to back the country into a corner

The statement, attributed to first vice minister of foreign affairs Kim Kye Gwan, continues: 'It is a ridiculous comedy to see that the Trump administration, claiming to take a different road from previous administrations, still clings to the outdated policy on the DPRK - a policy pursued by previous administrations at the time when the DPRK was at the stage of nuclear development.

'If President Trump follows in the footsteps of his predecessors, he will be recorded as more tragic and unsuccessful president than his predecessors, far from his initial ambition to make unprecedented success.

'If the Trump administration takes an approach to the DPRK-US summit with sincerity for improved DPRK-US relations, it will receive a deserved response from us.

'However, if the US is trying to drive us into a corner to force our unilateral nuclear abandonment, we will no longer be interested in such dialogue and cannot but reconsider our proceeding to the DPRK-US summit.'

DPRK is an acronym for Democratic People's Republic of Korea.

The statement takes particular issue with Bolton and his suggestion that the North follow a Libya-style program of disarmament.

Over a decade ago, Libya under then-ruler Muammar Gaddafi agreed to give up its nuclear and chemical weapons program - only to have the West lead a military effort to remove Gaddafi from power after the Arab Spring in 2011.

The regime branded that suggestion 'awfully sinister', saying it was an attempt to impose the 'miserable fate' of Iraq or Libya on the North.

'We shed light on the quality of Bolton in the past,' the statement adds, 'and we do not hide our feeling of repugnance toward him'.

'The world knows all too well that our country is neither Libya nor Iraq,' it said.

In an earlier statement, Kim's regime also attacked the ongoing 'Max Thunder' joint military exercises between the United States and South Korea, saying they are actually a 'rehearsal for invasion' of the North.

'The United States will also have to undertake careful deliberations about the fate of the planned North Korea-U.S. summit in light of this provocative military ruckus jointly conducted with the South Korean authorities,' KCNA said.

This photo from 2017 shows a vehicle carrying what appears to be an intercontinental ballistic missile during a military parade at Kim Il Sung Square in Pyongyang, North Korea

President Trump last week greeted three Americans who were released from North Korea as they returned in the wee hours of the morning to an air case in suburban Maryland

The White House made no immediate moves to slow down preparations for the summit on Tuesday.

White House Press Secretary Sarah Sanders simply said: 'We are aware of the South Korean media report. The United States will look at what North Korea has said independently, and continue to coordinate closely with our allies.'

President Trump ignored reporters asking for an update twice on Tuesday as he came and went from the White House to Walter Reed hospital, where his wife was recovering from a benign kidney surgery.

South Korea's Yonhap News Agency had earlier reported that Pyongyang also canceled high-level talks with Seoul, scheduled for later in the day.

The North Koreans cited the military drills as the reason.

The meeting was to happen in the border town of Panmunjom, as a followup to Kim's April meeting with his South Korean counterpart, Moon Jae-In.

The Trump administration has appeared to be making progress in recent weeks toward a new diplomatic framework with the hermit kingdom.

Tempers had cooled following months of belligerence on both sides – Trump called Kim 'Little Rocket Man' and Kim responded by branding him a 'mentally deranged U.S. dotard.'

Last week Secretary of State Mike Pompeo traveled to Pyongyang on a mission to retrieve three Americans held prisoner in the communist nation.

He returned a day later with Kim Dong Chul, Kim Hak-song and Tony Kim on board his government jet. Trump, eager to reap the PR benefit of a public splash, went to Joint Base Andrews in Maryland at 2:00 in the morning to greet them personally.

The prisoner release was seen as a first step toward the planned summit, which Trump announced last week would take place June 12 in Singapore.

The North Korean statement got a jump on the U.S State Department

U.S.-KOR Combine Force take part in an annual best warrior competition at U.S. military base Camp Casey in Dongducheon, South Korea, on 12 April 2018

'We have no information on that,' said spokeswoman Heather Nauert, NBC reported. 'Let's not get ahead of ourselves. We need to verify it.'

The snag comes after North Korea began dismantling a key nuclear test site just weeks before Kim due to meet Trump for what would be historic summit.

Satellite images examined by American researchers appear to show building demolitions, removal of railways, and overturned mining carts at the Punggye-ri nuclear test site in North Korea.

The researchers are relying on commercial satellite imagery from May 7, according to the 38 North web site.

The site analyzed images which show significant changes that have been made at the location which are consistent with decommissioning.

Critics have argued that the site already is in need of decommissioning, making its decommissioning less of a concession than it might otherwise seem.

'Between April 20 and May 7, 2018, the probable engineering office building and a possible instrumentation shed located just outside the North Portal (where the last five underground nuclear tests have been conducted) were razed along with at least two smaller buildings or sheds,' according to 38 North.

Meanwhile, the hermetic nation plans to join international efforts to implement a total ban on nuclear weapons tests, its ambassador told the United Nations today.

Pyongyang has pledged dismantle the test site some time between May 23 and May 25 in order to uphold its pledge to cease tests, its state media reported on Saturday.

No personnel or significant activity is observed at the barracks area

Earlier today, North Korea's ambassador to the UN in Geneva Han Tae-song announced the country's intentions to work towards a complete ban on tests.

'DPRK will join international desires and efforts for a total ban on nuclear tests,' Han Tae-song said in an address to the Conference on Disarmament, using North Korea's official acronym.

Han told the UN assembly that his country aimed to make more 'efforts to achieve the development of intra-Korean relations, defuse acute military tensions and substantially remove the danger of the war on the Korean peninsula.'

'It will make sincere efforts... to establish a durable lasting peace mechanism' with its neighbour to the south, he said, urging the international community to 'extend its active support in encouraging and promoting the current positive climate.'

The military exercises that apparently provoked the North Korean side are known as 'Maximum Thunder.' The drill involves F-15 and F-16 aircraft numbering more than 80, NBC News reported.

The annual drill has regularly been a thorn in the side of the North Koreans. U.S. military officials say it is needed to practice the kind of cooperation that would be necessary in any real live military situation on the heavily-armed Korean peninsula.

It includes both air-to-air and air-to ground mission practice.