North Korea has demanded the removal of US Secretary of State Mike Pompeo from nuclear talks, accusing him of "talking nonsense" and being "reckless".
A senior foreign ministry official said that further talks would be "lousy" if Mr Pompeo was involved, asking that he be replaced by someone "more careful".
It comes after North Korea said it had tested a new "tactical guided weapon".
The test is the first since a February summit in Hanoi between the countries' leaders ended without an agreement.
Mr Pompeo visited North Korea four times last year - including for a meeting with North Korean leader Kim Jong-un.
Last week, during a US Senate subcommittee hearing, Mr Pompeo was asked if he would agree with descriptions of Mr Kim as a "tyrant", he then responded: "Sure, I'm sure I've said that."
This was met with a strong reaction from North Korean foreign ministry official Kwon Jong-gun, who said that Mr Pompeo "spouted reckless remarks, hurting the dignity of our supreme leadership... to unveil his mean character".
Mr Kwon also blamed Mr Pompeo for the abrupt ending to the Hanoi summit.
On Thursday, he said that if Mr Pompeo were to be involved in further talks, "the table will be lousy once again and the talks will become entangled".
"Even in the case of possible resumption of dialogue with the US, I wish our dialogue counterpart would not be Pompeo but... [another] person who is more careful and mature in communicating with us," Mr Kwon said, according to the Korean Central News Agency (KCNA).
During discussions in Pyongyang in July, Mr Pompeo was condemned for his "gangster-like" insistence that the country move towards denuclearisation.