When U.S. President Donald Trump meets Chinese President Xi Jinping this week, their summit will be marked not only by deep policy divisions but a clash of personalities between America's brash "tweeter-in-chief" and Beijing's cautious, calculating leader.

They may have one thing in common: their rhetoric about restoring their nations to greatness. But the two men differ in almost every other respect, from their political styles to their diplomatic experience, adding uncertainty to what has been called the world's most important bilateral relationship.

Five months after his election on a stridently anti-China platform, Trump appears to have set himself on a course for collision rather than conciliation with Xi, raising doubts as to whether the world's two biggest economies can find common ground.