The Asianist

According to Chosun Ilbo, a major Korean daily:

North Korea is not ready to come back to six-party talks on its nuclear program this week because they sense a lack of trust, Thai Foreign Minister Kantathi Suphamongkhon said Sunday. After a meeting with North Korean Foreign Minister Paek Nam-sun in Pyongyang, Kantathi said, "The North Korean foreign minister told me what he had in mind, what had caused North Korea not to be able to participate in the six-party talks scheduled for Monday."

According to another report, North Korea, which blames the delay to US-South Korea military exercise, may return to the negotiation table "depend[ing] on the United States":

North Korean Foreign Minister Paek Nam-sun on Monday confirmed six-party talks on his country’s nuclear program could restart in mid-September.

Paek said the talks could return from recess "just before the end of September... If things are going well, mid-September is possible," Reuters reported.

The minister said the talks, which had been scheduled to reconvene this week, were being delayed due to annual South Korea-U.S. military exercises.