President Donald Trump has vowed to deliver an ultimatum to Chinese leader Xi Jinping to rein in North Korea when the two men meet for the first time this week. But Trump's early retreat on Taiwan already has chipped away at his standing with Beijing. Another bluff could leave him looking the way he hates most -- weak.

Trump enters the first U.S.-Chinese summit short on foreign policy experience. But his candor and unpredictability, combined with veiled threats of sanctions on Chinese banks and even U.S. military action against North Korea, could provide leverage. But if he's bluffing, and Xi calls him on it, that might prove damaging in future negotiations with China.

The two-day meeting at Mar-a-Lago starts Thursday after yet another North Korean test-launch of a ballistic missile.