North Korea continues to pursue nuclear and ballistic missile technologies but the United States does not believe it is in a position to “tip” one of them with a nuclear warhead, State Department spokesman John Kirby said on Tuesday. North Korea’s leader, Kim Jong-un, said on Sunday , raising the prospect of putting parts of the United States within range. “We do not believe that at this point in time he has the capability to tip one of these with a nuclear warhead … but we do know that he continues to want to have those capabilities and the programmes continue to march in that direction,” Kirby told reporters. Asked whether he would agree with president-elect Donald Trump’s assessment that China was not helping to contain North Korea’s nuclear ambitions, Kirby said: “We would not agree with that assessment.