For years the US and South Korea have conducted combat drills that both say are vital to defending the Korean Peninsula.
Pyongyang is also threatening to cancel a planned summit, the culmination of nearly six months of intense diplomacy, between US President Donald Trump and Kim on June 12.
The US is calling for the denuclearisation of the peninsula and a complete dismantling of North Korea’s nuclear weapons programme.
In its latest statement, North Korea said the US should stop asking for that unless Trump offers something in return.
But is North Korea likely to walk on the negotiation? Here is what we know:
The US administration said it is looking for irreversible denuclearisation and the total decommissioning of nuclear weapons, missiles and biochemical weapons in North Korea. Its formula is: “abandoning nuclear weapons first, compensating afterwards.”
North Korea has responded with anger. “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 … summit,” Kim Kye-gwan, North Korea’s first vice minister of foreign affairs, has said in a statement.
Kim Kye-gwan has also criticised comments by Trump’s top security adviser, John Bolton, and other US officials, who have said North Korea should follow the “Libyan model” of nuclear disarmament and provide a “complete, verifiable and irreversible dismantlement”.
Libya and North Korea: Libyan leader Muammar Gaddafi had a nuclear weapons programme, which he decided to scrap in 2003 in exchange for economic benefits after lengthy negotiations with the US. However, Gaddafi was killed eight years later, during the Arab Spring in 2011, partly with US help.
However, despite the threats, analysts believe it is unlikely that North Korea intends to scuttle all diplomacy. Most probably, it wants to gain leverage in advance of the talks between Kim and Trump.
The US and North Korea have struck deals over North Korea’s nuclear programme that have failed.
In April 2009, North Korea walked out of the six-party talks after the UN Security Council unanimously condemned it for launching a long-range rocket earlier that month. The talks were a series of multilateral negotiations that began in 2003 between North Korea and South Korea, Japan, the US, China and Russia aiming to end its nuclear programme peacefully.
Mike Pompeo, US secretary of state, and Kang Kyung-wha, South Korean foreign minister, had an emergency call on Wednesday.
On May 16, the White House said it was still hopeful the summit would take place, adding Trump was prepared for a tough negotiation.
“The president is ready if the meeting takes place,” Sarah Sanders, the White House spokesperson, told Fox News. “If it doesn’t, we’ll continue the maximum pressure campaign that’s been ongoing.”
On May 16, China urged North Korea not to cancel the historic summit. “We support the improvement of North-South (Korean) relations, the promotion of dialogue between North Korea and the US, denuclearisation on the peninsula and North Korea’s development of its economy,” Xi was quoted as saying by state broadcaster CCTV.