The leaders of China, Japan and South Korea say they will not tolerate further provocation from North Korea, amid fears that Pyongyang is preparing for a new nuclear test.
South Korean President Lee Myung-bak made the remark Sunday after meeting in Beijing with Chinese Premier Wen Jiabao and Japanese Prime Minister Yoshihiko Noda.
North Korea's failed rocket launch last month led to sanctions from the U.N. Security Council. The launch drew immediate condemnation from the United States and its allies, who view it as a disguised ballistic missile test barred under U.N. resolutions.
The three leaders decided Sunday to start free-trade negotiations before the end of the year. They also signed an investment agreement.
China, Japan and South Korea are the three largest East Asian economies.
Some information for this report was provided by AP, AFP and Reuters.