Pyongyang's UN Ambassador Kim Song is expected to make the speech on Sept. 30.

Ri's plan to travel to New York had spurred hope that he could meet with Pompeo on the sidelines of the UN session to discuss ways to move the stalled nuclear talks between the two countries forward.

The North's apparent decision not to send Ri came as the regime has sharply stepped up criticism of Pompeo.

Earlier this month, Ri himself issued a blistering statement slamming Pompeo as "the diehard toxin of the US diplomacy," and warned that the US would be "sadly mistaken" if it planned to continue its "confrontation" with the North through sanctions.

On Saturday, the North's first vice foreign minister, Choe Son-hui, also issued a statement rapping Pompeo for branding Pyongyang's behavior as "rogue." Choe warned that expectations for dialogue with the North are "gradually disappearing" and warned the communist regime could "reexamine all the measures we have taken so far." She also warned Washington not to test Pyongyang's patience.

Nuclear talks between the North and the US have been stalled after February's summit between US President Donald Trump and North Korean leader Kim Jong-un broke down without an agreement due to differences over sanctions relief and denuclearization measures.

Trump and Kim held a surprise meeting at the inter-Korean border on June 30 and agreed to resume working-level nuclear talks within weeks, but no such talks have taken place yet as Pyongyang conducted a series of missile and rocket launches. (Yonhap)