TOKYO (AP) — China’s announcement it has suspended North Korean coal imports may have been its first test of whether the Trump administration is ready to do something about a major, and mutual, security problem: North Korea’s nukes. While China is Pyongyang’s biggest enabler, it is also the biggest outside agent of regime-challenging change — just not in the way Washington has wanted.

Judging from Trump’s limited comments so far, and the gaping chasm between Washington’s long-held focus on sanctions and punishment and Beijing’s equally deep commitment to diplomatic talks that don’t require the North to first give up its arsenal, a deal between the two won’t come easily.

But if Beijing is indeed sending a signal to Trump about Pyongyang, its opening bid was a big one. North Korea’s coal exports to China totaled $1.2 billion last year, according to Chinese customs. U.S. officials say that represents about one third of the North’s total export income.

For Kim Jong Un, that’s going to hurt.