WASHINGTON — President Trump’s latest broadside against former Vice President Joseph R. Biden Jr. and his son Hunter appears to center on a joint venture that involved the younger Mr. Biden and some of China’s leading state-owned financial companies.

But the president’s claims bear little if any relation to the known facts.

Without presenting any evidence, Mr. Trump suggested on Thursday that China showered $1.5 billion on Hunter Biden in order to influence his father and win favorable trade deals with the United States.

“That’s probably why China for so many years has had a sweetheart deal where China rips off the U.S.A.” because they deal with people like “Biden where they give the son a billion and a half dollars,” Mr. Trump told reporters on the South Lawn of the White House. He added: “You know what they call that? They call that a payoff.”

Companies associated with Hunter Biden or his business partners have struck several deals involving China over the past decade. So, in fact, have Mr. Trump’s own relatives — a point that Mr. Trump does not mention in his now almost-daily accusations against the former vice president, a leading Democratic presidential candidate, and his son.