US sanctions alone cannot force China to get tough with NK: ex-sanctions official

"China will not be strong-armed into a course of action that it believes imperils its own national security," Szubin said. "For that reason, serious and high-level engagement with China will be needed to set out a way forward to include an intensive pressure campaign and the various scenarios that could follow from it, including potential leadership change in North Korea."

China won't take any chance when it comes to the North's fate, he said.

"Concerns over stability will be paramount. But I believe that our interests can be reconciled with China's," he said.

Szubin also said that sanctions can work against the North as long as they are enforced in earnest, especially by China.

"North Korea is not self-reliant or sanctions proof. Its leadership depends upon access to foreign imports and international banking services and that access can be disrupted," he said.

"Sanctions leverage over North Korea is concentrated in one country, China. If China is prepared to take a qualitatively tougher stance on sanctions against North Korea, sanctions have a chance to succeed."

He called for "a massive diplomatic investment and multilateral engagement" to marshal a campaign including China and other countries around the world.

"Even with a concentrated and strategic effort we obviously can't guarantee that a diplomatic effort powered by new sanctions pressure will succeed. But I believe that it has a real chance to do so. And I'm not aware of a better alternative," Szubin said.  (Yonhap)