US reveals new sanctions over North Korea's nuclear threat

She revealed the measures in South Korea during a visit to the border with the North.

They will target the sale or purchase of arms and related goods used to fund the communist regime's nuclear activities and the acquisition of luxury items to buy the loyalty of its elite.

Mrs Clinton and Defence Secretary Robert Gates toured the heavily fortified border in a symbolic trip four months after the sinking of a South Korean warship blamed on the North.

The penalties are intended to further isolate the North and persuade its leaders to return to talks aimed at getting it to abandon atomic weapons.

The US is also trying to forestall future provocative acts like the torpedoing of the Cheonan, which killed 46 South Korean sailors.

Specifics of the sanctions were still being worked out when Mrs Clinton and Mr Gates together toured the the demilitarised zone in the village of Panmunjom.

Under the gaze of North Korean guards, they paid tribute to the US, South Korean and international forces that patrol the world's last Cold War-era border. Sixty years after the fighting began, the peninsula remains divided in a state of war because the conflict ended in a truce, not a peace treaty.

Mr Gates said the visit was intended "to send a strong signal to the North, to the region and to the world that our commitment to South Korea's security is steadfast."

He added: "In fact, our military alliance has never been stronger and should deter any potential aggressor."

Both noted that since the Korean War, the South has become a major economic power while the North has become one of the poorest and most isolated dictatorships in the world.