BEIJING — President Trump came into office fuming about China. But lately he has been describing his Chinese counterpart, Xi Jinping, as if Mr. Xi were an old friend, even in dealing with deep divisions over North Korea.

“I believe he is trying very hard,” Mr. Trump said in an interview with Reuters on Thursday. “He is a good man. He is a very good man, and I got to know him very well.”

That’s heady praise for someone the president had never met before this month. But Mr. Trump’s time as a businessman may help make sense of his backslapping tributes to Mr. Xi.

In “Trump: The Art of the Deal,” his braggadocious memoir-cum-business playbook from 1987, Mr. Trump explained how he flattered, pummeled, cajoled and bluffed his way to what he wanted. He seems to hope to use the same tactics with China.