"Then, we will remain as the biggest threat to the US for long and long and will make it understand for sure what it has to do for the denuclearization," he added. "We are ready for both dialogue and stand-off."

He strongly criticized US Secretary of State Mike Pompeo for hampering talks and called him "the diehard toxin of the US diplomacy," citing a recent media interview in which Pompeo said that the toughest sanctions will be kept in place until the North gives up its nuclear weapons.

Pompeo said in a media interview earlier this week that he hopes North Korean leader Kim Jong-un will deliver on his commitment to denuclearize but added "in the event that he doesn't, we'll continue to keep on the sanctions that are the toughest in all of history."

"Is he really the man who begged for denuclearization and pledged the establishment of new DPRK-US relations when he was received by the chairman of the State Affairs Commission of the DPRK during his several visits to Pyongyang?" he said, referring to his previous trips to Pyongyang and meetings with North Korean leader Kim Jong-un.

"He is truly impudent enough to utter such thoughtless words which only leave us disappointed and skeptical as to whether we can solve any problem with such a guy," he added.

Friday's statement came a day after the North said it has no interest in talks as long as military threats continue, taking issue with Seoul's move to introduce F-35 stealth fighters from Washington. It also came after top US nuclear envoy, Stephen Biegun, said in Seoul on Wednesday that Washington is ready to resume talks with Pyongyang.

Biegun's trip, which coincided with the end of a joint military drill by Seoul and Washington, spawned speculation that the North and the US could soon resume working-level talks following a monthslong stalemate caused by the no-deal breakdown of their summit in February.

The summit fell apart as they failed to find common ground over Pyongyang's denuclearization steps and Washington's sanctions relief.

North Korea has beefed up criticism of South Korea and the US for heightening tensions by holding their summertime joint military exercise. Pyongyang has also slammed Seoul for its arms build-up, such as the introduction of the F-35A fighter jets. Seoul plans to deploy 40 F-35As through 2021.

On Wednesday, Biegun told reporters here that Washington is ready to resume stalled denuclearization talks as soon as he hears from his counterparts in North Korea.

Speculation arose that the US and North Korea might resume their denuclearization negotiations soon as US President Donald Trump earlier said that North Korean leader Kim expressed his willingness to resume talks once the military exercise between Seoul and Washington is over.

Trump and Kim agreed to restart working-level talks within several weeks when they met at the inter-Korean border on June 30.

The promised talks have not taken place amid tensions sparked by the North's recent series of weapons tests in protest of the Seoul-Washington military exercise.

Experts see the North's recent sharp-worded statements as expressing displeasure with Washington and apparently signaling that Pyongyang is not in a rush to resume bilateral nuclear talks.

Some see it as intended to strengthening its negotiation leverage before coming out for talks.

Seoul's unification ministry handling inter-Korean affairs urged Pyongyang and Washington to build mutual trust and respect in each other, hoping they could produce "good results" in their denuclearization talks. (Yonhap)