U.S. Secretary of State Hillary Clinton says Washington is considering putting North Korea back on its list of state sponsors of terrorism.

Clinton said during an interview with ABC News Sunday that the U.S. is attempting to find solid evidence of the North’s support for international terrorism, adding that Pyongyang has thwarted the purpose they were taken off the list to begin with.

Clinton said if the North is found to have transported nuclear materials to other countries by ship, the U.S. will take every action to interdict such efforts in the future and will move to block the flow of finances in and out of North Korea.

On reports that North Korean leader Kim Jong-il designated his youngest son, Jong-un, as his successor, Clinton said Washington is still assessing the situation.