Few news items over the past year had more entertainment value than one concerning the Onion and North Korean leader Kim Jong-un.

It was funny enough that the faux-news website named the double-chinned Kim the sexiest man of 2012. More entertaining still was that the People’s Daily, the stern mouthpiece of China’s Communist Party, fell for it.

Last week, another joke came at China’s expense, one straight from Kim. His nuclear test left his economic benefactors in Beijing flustered and the world wondering if North Korea was taunting China. Kim’s open act of defiance is a challenge for President Barack Obama and his plan to reduce the U.S.’s nuclear arsenal. But the real dupe here may Xi Jinping, who will become China’s president next month.

China has long viewed the Kim Dynasty as a useful hedge against U.S. influence. Yes, China’s leaders know the Kims are wacky, but they keep the West off balance. China won’t back Korean reunification because it means surrendering a vital bargaining chip and allowing the U.S. to have troops on its border.

Xi should end China’s unconditional support for North Korea’s tantrums and the shameful way it treats its 24 million people. China’s claims that it can’t rein in Pyongyang’s officials lack credibility. There is nothing to stop China from cutting Kim’s allowance. You want food and fuel? Then here are a few things you need to do in return for continued Chinese support.

First, Xi should demand that North Korea transform its economy and welcome international experts to help it upgrade industries such as agriculture, manufacturing and power. Insist that North Korea accept assistance from technocrats in China’s Finance Ministry to usher the country into the 20th century, never mind the 21st.

China fears a regime collapse that would lead to millions of North Koreans seeking refuge or that would inspire an Arab Spring among its own people. Well, how does allowing North Korea’s economy to atrophy further make that risk less acute? Xi might save China plenty of future problems by encouraging the modernization of its client state.

Second, he should join forces with Park Geun-hye, South Korea’s next president. Park pledged to improve relations with the North in ways only a person of her background can. In 1974, her mother was killed by North Korean agents in an assassination attempt on her father when he led the South. If Park can make nice with the Kim family, Xi could certainly meet her halfway and ensure that officials in Pyongyang are receptive.

Third, Xi must remember that China’s rise comes with commensurate responsibility. So does having a permanent seat on the United Nations Security Council, where China runs interference for its ally. North Korea’s latest nuclear test, its third, demands a robust Chinese response. At the very least, China must back real UN sanctions, not the flaccid ones now in place.

Think of the huge geopolitical points China would score by being a good global citizen. As the world’s most populous nation and second-biggest economy, China understandably wants a bigger say in world affairs. The route to more clout at the International Monetary Fund, World Trade Organization and other institutions runs through North Korea more than China’s leaders realize.

China should heed its blogosphere, which is pulsating with debate about the wisdom of supporting North Korea. If folks in the U.S. were annoyed that Kim tested a nuke on the same day as Obama’s State of the Union address, imagine how aggrieved mainlanders were that he did so during China’s Lunar New Year. Many consider it an unforgiveable affront.

The Internet is becoming harder for China to control at a time when anger is rising over income inequality. It would be bad news for Xi if the public and the Communist Party’s leaders lost patience over North Korea’s outbursts while China foots the bill. The last thing Xi wants is to be seen as Kim’s enabler at the expense of China’s global standing. If North Korea squeezed off a missile tomorrow, causing major destruction and loss of life, many would blame China for not doing more.

There comes a point where the cons outweigh the pros. China opposed Kim’s nuclear test, and he did it anyway. Xi will grapple with a long list of economic, diplomatic and social challenges while a giant bug buzzes around him. The days of swatting it away are long gone now that North Korea is a nuclear power, willing to blackmail governments with its arms while hiding behind China’s unconditional support.

It was impossible to keep a straight face while reading a Xinhua analysis, which argued that the U.S. and its allies forced Kim’s aggression last week by making him feel insecure. I found myself wondering if it were written by the jokesters at the Onion, not China’s official news agency.

Obama framed the issue in an intriguing way in his State of the Union speech: “The regime in North Korea must know they will only achieve security and prosperity by meeting their international obligations.” One could easily replace “North Korea” with “China” in that line.

Xi, for his part, wants the U.S. and China to forge a “new type of relationship between two great powers,” according to a speech he delivered last February. With North Korea, he has a perfect opportunity to make that more than a punch line. 

By William Pesek 

William Pesek is a Bloomberg View columnist. The opinions expressed are his own. ― Ed.