AZUZ: One challenge ahead of President Trump and Xi is their disagreement over how to pressure North Korea, and they'll have more than that to talk about. They're the leaders of the two largest economies on the planet. Their nations are both regional powerhouses. Will two nations that are an ocean apart be able to find common ground?

MATT RIVERS, cnn CORRESPONDENT: The United States and China, perhaps the most consequential relationship in the world today. But if that's the case, then what's at stake?

Let's start with the standoff on the Korean Peninsula. Both China and the United States agree that North Korea's nuclear weapons program is bad news.

They disagree on how best to stop it.

The U.S. thinks China should use its economic leverage to force North Korea to halt its testing program. China says the only way to solve the problem is the U.S. directly negotiates with the regime. It's a situation where tens of millions of lives are at stake, how will China and the U.S. can work together is key to solving the crisis.

Next, consider the Chinese and American economies, combined worth about 40 percent of global GDP. They are inextricably linked, with hundreds of billions of dollars in goods traded each year. But any barriers to that trade would mean that both economies would suffer. That in turn would hurt the global economy overall.

Finally, let's turn to the South China Sea. Over the last few years, China has aggressively built up artificial islands, extending its military capability far beyond its own borders. In response, the U.S. has sent warships near Chinese claimed territory. So, will China continue its expansion? Does the U.S. draw a red line in response? The answers will help shape the future of a volatile region.