Top envoys from Japan, the United States and South Korea held a trilateral dialogue Tuesday aimed at discussing measures to "maximize" pressure on North Korea over its nuclear and missile programs.

Kenji Kanasugi, director-general of the Foreign Ministry's Asian and Oceanian Affairs Bureau, told reporters that the three countries agreed to further cooperate in their effort to take "resolute" actions against nuclear provocations by the North. Kanasugi said the trio also shared the recognition that China — the largest trade partner with the North — has a "significant" role to play in reining in Pyongyang's saber-rattling. He did not elaborate.

South Korea's envoy on North Korean nuclear issues, Kim Hong-kyun, warned that Pyongyang's failure to discontinue its missile and atomic tests will be met with "unbearable" punitive sanctions, and that the three countries will seek to "maximize" pressure against the reclusive state.

Kanasugi is scheduled to meet his visiting Chinese counterpart, Wu Dawei, special representative for Korean Peninsula Affairs, on Wednesday. In meeting with Wu, Kanasugi said he will discuss the possibility of China cutting off its supply of oil to North Korea.

Meanwhile, the three envoys agreed to "continue to work very closely with China" and "coordinate all actions — diplomatic, military, economic — regarding North Korea," Joseph Yun, special representative for North Korea policy from the U.S., told reporters after the meeting.

“We really do not believe North Korea is ready to engage us toward denuclearization,” Yun said. “We make clear among ourselves that denuclearization remains the goal and we very much want North Korea to take steps toward that.”

Yun noted that U.S. Secretary of State Rex Tillerson will hold a ministerial meeting in New York with members of the U.N. Security Council on Friday that "will be devoted to North Korea issues."