Clinton, speaking at a joint news conference in Seoul after holding unprecedented security talks with US and South Korean defence and military officials, said the sanctions were part of measures designed to rein in the regime's nuclear activities by stamping out illegal moneymaking ventures used to fund the program.
"These measures are not directed at the people of North Korea, who have suffered too long due to the misguided priorities of their government," Clinton said. "They are directed at the destabilising, illicit, and provocative policies pursued by that government."
The UN Security Council has imposed stiff sanctions on North Korea in recent years to punish the regime for defying the world body by testing nuclear weapons and long-range missiles, and illegally selling arms and weapons.
With few allies and diminishing sources of aid, impoverished North Korea is believed to be turning to illicit ventures to raise much-needed cash. Pyongyang also walked away last year from a disarmament-for-aid pact with five other nations that had provided the country with fuel oil and other concessions.
Clinton, making a high-profile trip to South Korea with Defence Secretary Robert Gates just four months after the deadly sinking of a South Korean warship, urged North Korea to turn away from its path toward continued isolation.