Joe Biden made light of President Trump's claim his lobbyist son Hunter Biden earned "billions of donors" in China as Trump comes under fire for suggesting that the communist country investigate the family of a potential political rival.

“I wonder where the hell that money is man because I’ve got to pay tuitions. God bless me!” Biden joked with about 70 donors gathered at a San Francisco venture capital firm on Thursday.

Biden similarly referenced the money in jest at an earlier fundraiser Thursday hosted by Sen. Dianne Feinstein of California: “He said my son made a billion dollars in China. I don’t know where the hell it is.”

Trump stoked outrage on Thursday when he told reporters the Ukrainian government should "start a major investigation into the Bidens" as House Democrats ramp up their impeachment inquiry into whether the president leveraged military aid to pressure Ukraine into digging up dirt on the Bidens. Joe Biden is a top-tier candidate for the 2020 Democratic presidential nomination.

"Likewise, China should start an investigation into the Bidens because what happened in China is just about as bad as what happened with Ukraine," Trump said. "I'm sure that President Xi does not like being under that kind of scrutiny where billions of dollars is taken out of his country by a guy that just got kicked out of the Navy," he added of Chinese leader Xi Jinping and Hunter Biden. "He got kicked out of the Navy, all of a sudden he's getting billions of dollars. You know what they call that? They call that a pay off."

Joe Biden threatened to withhold $1 billion in U.S. loan guarantees during a 2016 trip to Kiev if Ukraine didn't fire its top prosecutor. Trump allies, such as his personal lawyer Rudy Giuliani, claim there was a potential conflict of interest because the prosecutor had looked into Burisma Holdings, an oligarch-owned energy company that paid Hunter Biden $50,000 a month as a board member.

Hunter Biden, a Georgetown University and Yale Law School graduate, has been subjected to unwanted media attention in the past not only for his foreign ties, but also when he was discharged from the Navy Reserve in 2014 for testing positive to cocaine. The younger Biden has connections to Patrick Ho, a high-ranking Chinese businessman who was charged by the Justice Department with global corruption and bribery in 2017.

A Biden campaign spokesman didn't immediately return the Washington Examiner's request for comment regarding whose tuition the former vice president is still paying.

Other than his eldest son, Beau Biden, who died in 2015 from an aggressive form of brain cancer at the age of 46, and Hunter Biden, 49, both of whom he had with his first wife, the late Neilia Biden, the Delaware senator for 36 years and his second wife, Jill Biden, have a daughter, Ashley Biden, 38. He also has five grandchildren: Naomi, 25, Finnegan, 21, Maisy, 19, Natalie Biden, 15, and Hunter Jr., 13.