"If they're not willing to do it, then I think President Trump has been very clear… they're not going to get relief from the crushing economic sanctions that have been imposed on them and we'll look at ramping those sanctions up in fact," said Bolton.
READ MORE: Hanoi Trump-Kim Summit Has Set Back DPRK Denuclearization — Pundit
Earlier, US State Department Deputy Spokesperson Robert Palladino said in a press release that US Secretary of State Mike Pompeo briefed the foreign ministers of China, South Korea and Japan on President Donald Trump's Hanoi summit with North Korean leader Kim Jong-un. He also added that Pompeo and South Korean Foreign Minister Kang Kyung-hwa, during a phone conversation, agreed to closely coordinate on the denuclearization of the Korean peninsula.
The two-day summit in Vietnam's Hanoi between US President Donald Trump and North Korean Leader Kim Jong-un ended abruptly on 28 February without them reaching an agreement.