By now, Xi Jinping is used to Donald Trump's tariff threats. But the U.S. president's latest ultimatum is personal, and the Chinese leader's response could have far-reaching consequences for his political future.

Trump on Monday said he could impose tariffs "much higher than 25 percent" on $300 billion in Chinese goods if Xi doesn't meet him at the upcoming Group of 20 summit in Japan. China's foreign ministry — which usually refuses to provide details of meetings until the very last minute — declined Tuesday to say whether the meeting would take place.

The brinkmanship puts Xi — China's strongest leader in decades — in perhaps the toughest spot of his six-year presidency. If Xi caves to Trump's threats, he risks looking weak at home. If he declines the meeting, he must accept the economic costs that come with Trump possibly extending the trade conflict through the 2020 presidential election.