Now that U.S. President Donald Trump's strategy of pressuring China to rein in North Korea's nuclear and missile programs has failed, Washington's options are narrowing. The recent passage of a set of sanctions against Pyongyang by the United Nations Security Council may have given the U.S. some temporary breathing space before taking further steps to squeeze the Kim Jong Un regime. However, if Kim continues his provocative nuclear and missile tests, the U.S. may have to turn back to China and try arm-twisting to accomplish what Trump's sweet talk couldn't. At the moment, the most-talked about option is secondary sanctions against Chinese entities doing business with North Korea.

On the surface, the logic behind a "get tough" approach to China sounds impeccable. As Pyongyang's principal patron, China keeps the Kim regime on life support with trade and thus bears primary responsibility for preventing the rogue state from endangering the world. If Beijing continues its current course of shielding Pyongyang from external pressure, it will have to pay a real price. Secondary sanctions would make Chinese leaders appreciate the costs of their ill-advised policy.

Like all the other options proposed to deal with North Korea, secondary sanctions against China sound promising in theory but would be devilishly complicated when put in practice. By refusing to turn up the heat on North Korea after Trump explicitly tied the future of U.S.-China relations to Beijing's policy toward Pyongyang, Chinese leaders have obviously considered -- and accepted -- the likely consequences of their decision, including secondary sanctions.

From Beijing's perspective, the costs of potential secondary sanctions are less than those associated with an economic collapse of North Korea that might be triggered by a total cut-off of Chinese support. If, as Trump desired, China shuts off its oil pipeline, ends all trade, and blocks North Koreans from its banking system, the regime will slowly wither, significantly raising the odds of its eventual collapse. However, as is well known, the geopolitical fallout from the disappearance of North Korea as a strategic buffer for China is too horrifying for Chinese leaders to contemplate.