President Donald Trump said in a late-night social media post that Chinese leader Xi Jinping was very tough to make a deal with, raising questions about whether a fragile economic truce between the world’s two largest economies will hold.

Mr. Trump said in a post on Truth Social that his call with Xi Jinping, China’s top leader, had focused entirely on the trade relationship between the nations, which has soured in recent months in a dispute over the export of critical minerals used in an array of industries.