US officials want to restart denuclearization talks with their North Korean counterparts, but observers say Pyongyang has put the ball back into US President Donald Trump's court.

North Korea's chief negotiator is demanding that the United States guarantee its security and lift sanctions, warning that otherwise, it could resume tests of nuclear weapons and intercontinental ballistic missiles. Kim Myong Gil made the comments on Saturday after meeting with US Special Representative for North Korea Stephen Biegun near the Swedish capital of Stockholm.

Kim said the working-level talks had "broken off" and blamed the US side for being inflexible and sticking to their previous stance. The talks, which lasted eight and a half hours, were the first of their kind since a meeting of the leaders of the two countries ended without agreement in Hanoi, Vietnam in February. Meanwhile, the American side has a different take on Saturday's meeting. A State Department spokesperson said in a statement that "the US brought creative ideas," suggesting that the American delegation made new proposals regarding Pyongyang's denuclearization steps and rewards.

Observers say the two sides were unable to approach an agreement due to the North Korean delegation's hardline stance. American officials have accepted an offer from Sweden to host another meeting in two weeks. But the North Korean side has said that will depend on the US position.

NHK