UNITED States president Donald Trump is on tour, visiting the leaders of Japan, South Korea and China, and the same topic will dominate all three conversations - North Korea.
Japan's Prime Minister Shinzo Abe and South Korea's President Moon Jae-in will welcome reassurance that the US will protect them from North Korea's nuclear weapons but, in Beijing, Trump is the supplicant.
The American president will be asking President Xi Jinping to do something, ANYTHING, to make North Korea stop testing nuclear weapons and intercontinental ballistic missiles. Trump has painted himself into a corner with his tongue, but even he knows (or at least has been told many times by his military advisers), that there is no military solution to this problem that does not involve a major war, and probably a local nuclear war.
Trump promised that North Korea would never be able to strike the United States with nuclear weapons, and the reality is that it will get there quite soon (if it is not already there). The United States has no leverage over North Korea except the threat of war, so he needs China to get him off the hook.
China has lots of leverage: 90 per cent of North Korea's imports come in through China, and most of its foreign exchange comes from selling things to China. Beijing could leave the North Korean population freezing and starving in the dark if it chose - but it won't do that.
Xi Jinping may throw Donald Trump a couple of smallish fish - a ban on the sale of hair dryers and chainsaws to North Korea, perhaps - but he won't do anything that actually threatens the survival of the North Korean regime. Yet he knows that nothing less will sway Kim Jong-un, because the North Korean leader sees his nukes and ICBMs as essential to the survival of the regime.