North and South Korea are set to separately address the U.N. Security Council Monday to discuss the March sinking of a South Korean warship that killed 46 sailors.
South Korea's president has called for a stern response to the deadly sinking of the Cheonan, which an international investigation has blamed on North Korea.
In a televised address Monday, President Lee Myung-bak said another attack could happen at any time if South Korea and the international community failed to respond.
North Korea has denied any involvement in the incident, and has said any retaliation would lead to war.
South Korea will brief Security Council members Monday on its investigation into the sinking. Representatives from North Korea plan to explain their position on the incident afterward.
South Korea's president also said Monday that he will hold some of his military officers responsible for the sinking.
That announcement comes one day after the chairman of the Joint Chiefs of Staff, Lee Sang-eui, offered his resignation.
South Korean investigators last week said Lee Sang-eui and at least 22 other officers should be punished for mishandling the sinking.
The two Koreas technically remain at war because a 1953 armistice that ended the three-year Korean War was a truce, not a formal peace treaty.
Some information for this report was provided by AP and Reuters.