Beijing — It's up to Washington to alter its approach if it wants more talks with North Korea, Pyongyang's chief nuclear negotiator said Monday after weekend discussions between the sides broke down amid acrimony. Kim Myong Gil made the remarks at Beijing's airport on his way back to North Korea following talks with his U.S. counterpart, Stephen Biegun, on Saturday that Kim described as "very bad and sickening."

"Whether or not there are further talks will depend on the U.S.," Kim told reporters.

"Whether there will be any shocking actions that nobody would expect to see if the U.S. is not ready, nobody knows. Let's wait and see," he said.

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On Sunday night, North Korea's Foreign Ministry issued a statement accusing the U.S. of trying to mislead the public and "spreading a completely ungrounded story that both sides are open to meet" again.

North Korea's chief nuclear negotiator Kim Myong Gil is seen outside the North Korean embassy in Stockholm, Sweden, October 5, 2019. REUTERS

The Stockholm talks "made us think they have no political will to improve (North Korea)-U.S. relations and may be abusing the bilateral relations for their own partisan interests" at home, the statement said.

Saturday's talks were the first since the second summit between President Donald Trump and North Korean leader Kim Jong Un collapsed in Vietnam in February due to squabbling over how much sanctions relief should be given to the North in return for dismantling its main nuclear complex.

The two leaders held a brief, impromptu meeting at the Korean border truce village of Panmunjom in late June and agreed to restart diplomacy.

Sweden invited North Korea and the U.S. to come back to Stockholm in two weeks for another round of negotiations. Sweden often acts as a bridge between Washington and Pyongyang because the U.S. does not have official diplomatic relations with North Korea.

While the North has shown itself receptive to talks without preconditions, Kim, the chief negotiator, sounded skeptical in his remarks about the chances for future success.

"It has been almost 100 days since the leaders' meeting in Panmunjom and (the U.S. has) not presented any new initiative. Do you think they will come up with a new one in two weeks?" Kim told reporters after being asked if North Korea would accept the invitation.

North Korea has demanded the United States come up with mutually acceptable proposals to salvage the nuclear diplomacy by the end of this year.

U.S.-led diplomacy on how to rid North Korea of its nuclear weapons collapsed after Mr. Trump rejected Kim's demand for sweeping sanctions relief in return for partial disarmament steps during their Vietnam summit.

Many experts say recent weapons tests by North Korea were mainly aimed at applying pressure on the United States ahead of a possible resumption of talks.

Most of the weapons tested were short-range missiles and rockets that experts said could target South Korea, not the mainland U.S.

Just last week, however, North Korea conducted what appeared to be its first test of a missile capable of being fired from underwater in three years. A U.S. official told CBS News senior national defense correspondent David Martin that the North had conducted a land-based test of a mid-range, submarine launched ballistic missile (SLBM).

CBS News correspondent Ramy Inocencio reported the test launch was a significant escalation from the short-range missiles North Korea has tested so far this year. North Korea having the ability to launch missiles from submarines would be alarming because such weapons are much harder to detect in advance.