The warning came two days after the U.N. Security Council unanimously approved new sanctions to punish North Korea, including a ban on coal and other exports worth over $1 billion.
Earlier, U.S. Secretary of State Rex Tillerson said new United Nations sanctions targeting North Korea are a "very good outcome".
Indeed, North Korea reportedly requested bilateral talks with several countries during the forum, but Foreign Minister Ri Yong-ho was met only by the foreign minister of chair country the Philippines after the ASEAN member countries chose to avoid individual contact.
North Korean Foreign Minister Ri-Yong Ho arrives at his hotel in Manila on August 7, 2017, after attending ASEAN meetings hosted by the Philippines.
Last week, Mr Tillerson said North Korea needed to cease both its missile launches and nuclear weapons tests for talks to begin.
Top diplomats from Asia-Pacific countries expressed "grave concern" on Tuesday over North Korea's escalation of regional tensions and urged it to comply with U.N. Security Council resolutions. He said the North could still carry out further missile tests or a sixth atomic bomb test in the coming months under its broader weapons development timetable.
The UN Security Council on Saturday imposed its toughest round of sanctions yet against Pyongyang over its two intercontinental ballistic missile (ICBM) tests in July.
The latest United Nations resolution bans North Korean exports of coal, iron, iron ore, lead, lead ore and seafood. The North Korean was spotted at the gala smiling and toasting with the other foreign ministers.More news: Virginia governor to white nationalists: 'Go home ... Shame on you'
More news: UK Expected To Unveil Post-Brexit NI Border Plan This Week
More news: Global Stocks Selloff Stops at Wall Street; Gold, Yen Tick Up
Tillerson says the US has "other means of communication" open to North Korea if the country wants to express to the USA a desire to talk.
The minister also praised the remarks of US Secretary of State Rex Tillerson, after the US made a series of guarantees including it did not seek a regime change in North Korea or an accelerated reunification of the Korean peninsula.
"And we hope, again, that this ultimately will result in North Korea coming to the conclusion to choose a different pathway, and when the conditions are right that we can sit and have a dialogue around the future of North Korea so that they feel secure and prosper economically".
North Korea provided reporters with a copy of his statement as Ri returned to his hotel Monday evening.
China, however, is easily North Korea's biggest trading partner and economic benefactor, and helped design the sanctions package.
"What we have to do is everything we can to pressure this regime, to pressure Kim Jong-un and those around him such that they conclude, it is in their interest to denuclearize", he said.
Susan Thornton is the top USA diplomat for Asia.
The meeting comes as the US and Asian nations join together to try to step up Pyongyang's economic and diplomatic isolation.