The top US official on East Asia has warned North Korean leader Kim Jong-un could face death if he attempts to use nuclear weapons, stressing the nuclear program undermines his security rather than strengthening it.

"Put yourself in Kim Jong-un's place. That is not a good place to be. Perhaps he's got an enhanced capacity to conduct a nuclear attack and then immediately die. But that can't be plan A," Russel said during a meeting Wednesday with US defense reporters, according to an AP report.

Russel was also quoted as saying that the US reserves the right to punish Chinese companies that violate UN sanctions on the North unless China punishes them.

"To the extent that the Chinese authorities themselves take action against North Korea malefactors or Chinese companies that are collaborating with North Korea, then there's no cause for action by the United States or others," Russel said, according to AP.

"Where they don't take action, the United States reserves the right under UN Security Council resolution 2270 or under our own national authorities to take action," he said, referring to the latest package of sanctions adopted after the North's January nuclear test.

Last month, the US Treasury Department blacklisted China's Dandong Hongxiang Industrial Development Co. Ltd., its owner and three other company officials in a landmark move representing the first-ever sanctions on a Chinese entity over Pyongyang's weapons programs.

Officials have said that they are investigating more Chinese firms.

Russel stressed that Washington and Beijing are cooperating on North Korea, adding that the US is constantly "scanning the horizon" for evidence of sanctions violations and makes a point of sharing with China first any information they have about "bad actors" there, according to AP. (Yonhap)