File Photo: Top leader of the Democratic People's Republic of Korea (DPRK) Kim Jong Un (L) meets with U.S. President Donald Trump in Singapore, on June 12, 2018. (Xinhua/Ministry of Communication and Information of Singapore)

WASHINGTON, March 5 (Xinhua) -- 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 United States 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."

"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."

President Donald Trump and Kim Jong Un, top leader of the DPRK, ended their second summit in Hanoi on Feb. 27-28, without reaching an agreement.

Nevertheless, the White House said the two leaders had "very good and constructive meetings" and discussed various ways to "advance denuclearization and economic driven concepts."