U.S. National Security Adviser John Bolton said late Tuesday that the United States would step up sanctions against the Democratic People's Republic of Korea (DPRK) if Pyongyang was unwilling to abandon its nuclear weapons program.

In an interview with FOX Business Network, Bolton said that the U.S. would see whether the DPRK was still serious about negotiations and was committed to giving up its "nuclear weapons program and everything associated with it".

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"If they're not willing to do it... 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," he added.

Bolton said in another interview on Sunday that Washington's "program of maximum pressure will continue" on Pyongyang, which had "brought them to the table in the first place".

Bolton's remarks came after U.S. Secretary of State Mike Pompeo said Monday that he was hopeful the U.S. would send a delegation to the DPRK in the coming weeks.

Meanwhile, Republic of Korea (ROK)'s top nuclear envoy Lee Do-hoon on Wednesday headed to Washington to consult with U.S. special representative for DPRK Stephen Biegun and other U.S. officials on measures to resume U.S. – DPRK talks, ROK's Foreign Ministry said Tuesday.

Trump and Kim ended their second summit in Hanoi on February 28, without reaching an agreement, but both sides agreed to continue "productive talks to discuss denuclearization."

(Cover: U.S. National Security Advisor John Bolton speaks in Washington, DC, December 13, 2018. /VCG Photo)