South Korean analysts warn North Korea will keep up nuclear tests in the new year, despite tougher sanctions.
The United Nations Security Council unanimously passed sanctions against the North last week for a ballistic missile test conducted in November.
South Korea's government predicts the North will conduct at least one test next year to try to master warhead re-entry before the new U.N. penalty takes a toll on the country's economy.
U.S.-based experts have predicted the North could be two to three tests away from a combat-ready nuclear weapon. But an American official also noted besides re-entry, the North hasn't mastered missile guidance and targeting.
North Korea has called the latest U.N. sanctions an "act of war."