North Korean Foreign Minister Ri Yong-ho will reportedly not attend an Association of Southeast Asian Nations(ASEAN) political and security forum set for early next month in Thailand. 

A diplomatic source said on Thursday that North Korea recently informed Thai officials that Ri will not attend the ASEAN Regional Forum set to open on August 2 in Bangkok.

If confirmed, it would mark the first time a North Korean foreign minister has missed the annual forum since 2003. North Korea is expected to send a senior official in Ri’s stead.

North Korea and the U.S. were widely expected to meet on the sidelines of the forum as part of efforts to restart working-level denuclearization talks with Pyongyang. 

The two sides agreed to resume working-level talks during an impromptu meeting between their leaders at the inter-Korean border on June 30, but little progress appears to have been made since then.