The United States has told North Korea that is must start shipping nuclear weapons, fissile material and some of its long-range missiles out of the country within a couple of months of the June summit between Kim Jong-un, the North Korean leader, and President Donald Trump, according to South Korean media.

The report by Yonhap News echoes comments by John Bolton, the president’s national security adviser, who on Sunday reiterated that Pyongyang could expect no assistance or relaxation of sanctions until it fully dismantles its nuclear and ballistic missile programmes.

Speaking on ABC News, Mr Bolton said, “I think the implementation of this decision means getting rid of all the nuclear weapons, dismantling them, taking them to Oak Ridge, Tennessee”.

The Oak Ridge National Laboratory is a nuclear research and storage facility that already holds key components from Libya’s nuclear weapons programme.

Yonhap said Washington’s demand was delivered to North Korea as part of the preparatory talks ahead of the summit meeting in Singapore between Mr Kim and Mr Trump, with the US stating that sanctions will remain in place until the North complies.