Appearing on CTV News, Carnegie's James Acton pointed out that  there is not much that can be achieved with sanctions on North Korea without China, and there is a big question over how willing China would be to exert serious sanctions on North Korea.

"They might add a name to a watchlist here or an organization to a watchlist there," said Acton, "but at the end of the day I think the Chinese are not willing to use whatever clout they have because they don't view the collapse of the North Korean regime in their interest."

Acton argued that it's time for a pivot in U.S. policy in this regard becasue efforts to denuclearize North Korea have proven futile and negotiations toward that goal fruitless. "What I think the Chinese can help on, and may be more willing to help on, is preventing North Korea from selling its technology to the highest bidder abroad," said Acton. "So I think we need a pivot from denuclearization to nonproliferation."

Acton pointed out that we don't know whether this device was plutonium or highly enriched uranium yet, but if it was highly enriched uranium, then that's a demonstration that North Korea has the capability to build relatively large nuclear weapons in relatively short period of time. "No one can turn back the clock," concluded Acton, "North Korea has clearly decided that it is in its strategic interest."