Officially, China is North Korea’s biggest ally and trading partner. But behind the scenes, Beijing may be getting uneasy with its neighbor’s bellicose baiting of the US.

North Korea is possibly preparing another missile test, or potentially a launch, though this is not viewed as a serious threat to America. Yet rather than backing Pyongyang, Beijing has expressed serious concerns over the mounting conflict with the US.

Meanwhile, American moves to bulk up its defenses in the region are probably unsettling China. The US has flown B52 bombers over South Korea and sent missile destroyers to waters off the Korean peninsula. And Beijing is likely getting increasingly uncomfortable with this heightened US military presence in its own backyard.

China’s own defence capabilities are believed not yet to be that advanced. But the nation has been working up what it calls an anti-access capability, which is supposedly (pdf p.358) a system of missiles, aircraft and submarines designed to defeat any potential military intervention by the US should China go to war with Taiwan. As The Diplomat writes here, the increased American presence in the Korean peninsula could make China nervous or give its military planners a sudden inferiority complex as they worry their anti-access capabilities no longer seem strong compared to what the US has sent to patrol its environs.

And a groundswell of opinion is building within China that the nation should dump its unruly neighbor. A mainland Chinese journalist based in Hong Kong told me recently that her countrymen no longer think of North Korea as a close ally, as this is a “cold war mentality” with which younger people in particular no longer identify.

Deng Yewun, an editor of a Communist party journal, wrote in the Financial Times in late February that China should abandon North Korea. He was later suspended from his job for putting that strong opinion into print. Yet the Chinese government-run media is still not exhibiting much support of Pyongyang.

This March 31 article (Chinese) in state news agency Xinhua made light of Pyongyang’s threats of war by saying “most political analysts believe that the declarations of war will stay on North Korea’s lips. It is improbable they are really going to act.”

Beijing will probably continue reluctantly propping up the Pyongyang regime to some extent. If it were to collapse, a flood of North Koreans desperate to escape their country would undoubtedly try to enter China.

But China also does not want a scenario where the two Koreas unify with American support, as that would mean a large US ally sitting on China’s doorstep.

That said, the Beijing leadership and the Chinese public are definitely souring on North Korea. China is the renegade nation’s largest source of arms, food and fuel. Pyongyang could well lose future advantages in that crucial relationship by continuing to annoy Beijing.