The US, South Korea and Japan are to hold talks in Washington shortly on ways to deal with North Korea.
China's president earlier warned US President Barack Obama that tensions on the Korean peninsula could get out of control if not properly handled.
It comes two weeks after North Korea's deadly attack on a South Korean island in answer to military drills by Seoul.
The International Criminal Court says it will investigate whether the act constituted war crimes by the North.
In a statement, the Court said it would examine the shelling of Yeonpyeong island on 23 November, in which two South Korean marines and two civilians were killed.
The situation on the peninsula remains highly uncertain. On Monday, South Korea pushed ahead with a new series of major live-fire exercises despite warnings from the North.
The drills are spread off South Korea's east, west and southern coastlines; the most contentious area, along the disputed western sea border, has been largely excluded.
South Korea's new defence minister has said he would use air strikes against the North if it attacked civilians again. BBC News
