North Korea’s chief negotiator called the South Korean government “ignorant and incompetent” on Thursday, denounced U.S.-South Korean air combat drills and threatened to halt all talks with the South unless its demands are met, Reuters reported.

The comments by Ri Son Gwon, chairman of North Korea’s Committee for the Peaceful Reunification of the country, were the latest in a string of inflammatory statements marking a drastic change in tone after months of easing tension with plans for denuclearisation and a summit scheduled with the United States.

Ri criticized the South for participating in the drills, as well as for allowing “human scum” to speak at its National Assembly, the North’s KCNA news agency said in a statement.

“Unless the serious situation which led to the suspension of the north-south high-level talks is settled, it will never be easy to sit face to face again with the present regime of south Korea,” the statement said. 

“On this opportunity, the present south Korean authorities have been clearly proven to be an ignorant and incompetent group devoid of the elementary sense of the present situation,” Ri’s statement said.