President Trump said Thursday that China should investigate the business dealings of 2020 rival Joe Biden's son, Hunter, as he doubled down on his prior -- and controversial -- call for Ukraine to do the same.

Trump struck a characteristically defiant tone while speaking to reporters on the White House South Lawn, en route to Florida.

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"China should start an investigation into the Bidens because what happened with China is just about as bad as what happened with Ukraine," Trump said. "I’m sure that President Xi [Jinping] 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."

His call for a Chinese investigation into the Bidens comes as the House moves forward with an impeachment inquiry against Trump for pressing Ukrainian President Volodymyr Zelensky over the summer to "look into" the family's dealings -- referring to an old investigation involving gas company Burisma Holdings where Hunter served on the board, and the elder Biden's role ousting a prosecutor who had been looking into them.

With his China comments, Trump was referencing another side-plot involving the former VP's son -- including a 2013 trip to Beijing on Air Force Two in which Hunter Biden tagged along. While it is not unusual for families to join such trips, NBC News reported that Hunter Biden was attempting to start a big-money private equity fund — Chinese authorities issued the business license for the fund 10 days after the trip was over.

Then-Vice President Joe Biden (L) waves as he walks out of Air Force Two with his granddaughter Finnegan Biden and son Hunter Biden at the airport in Beijing December 4, 2013. 

Then-Vice President Joe Biden (L) waves as he walks out of Air Force Two with his granddaughter Finnegan Biden and son Hunter Biden at the airport in Beijing December 4, 2013.  (Reuters)

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Biden campaign Chairman Cedric Richmond dismissed Trump's comments on China, saying it is a reprisal of his Ukrainian efforts to taint Biden and a reflection of polling showing Biden leading Trump in a hypothetical head-to-head matchup.

"This president is scared, and he's acting out," the Louisiana congressman said.

The Biden campaign charged that Trump's comments were "equivalent" to his call in 2016 for Russia to release Democratic nominee Hillary Clinton's emails if they had obtained them by hacking — which U.S. intelligence agencies later assessed to be the case. Biden communications director and deputy campaign manager Kate Bedingfield called it "a grotesque choice of lies over truth and self over the country."

Rep. Adam Schiff, D-Calif., tweeted Thursday that Trump's comments underscore the importance of the impeachment investigation he is now helping lead.

"The President cannot use the power of his office to pressure foreign leaders to investigate his political opponents," he said. "His rant this morning reinforces the urgency of our work. America is a Republic, if we can keep it."

The money figure cited by Trump has been disputed by a spokesman for Hunter Biden. The Washington Post recently reported that the firm behind the fund said they planned to raise $1.5 billion, but a spokesman said Hunter Biden bought only a 10 percent equity interest in the fund that was actually worth $430,000.

Nonetheless, Trump said Chinese authorities should look into Hunter Biden's business dealings in their country.

"He got kicked out of the Navy," Trump told reporters Thursday. "All of a sudden he’s getting billions of dollars. You know what they call that? They call that a payoff.”

Chinese President Xi Jinping makes a toast after delivering his speech at a dinner marking the 70th anniversary of the founding of the People's Republic of China at the Great Hall of the People in Beijing, Monday, Sept. 30, 2019. President Donald Trump said Thursday that he has not asked Xi to investigate the Biden family's business dealings, but that, "it's certainly something we could start thinking about."

Chinese President Xi Jinping makes a toast after delivering his speech at a dinner marking the 70th anniversary of the founding of the People's Republic of China at the Great Hall of the People in Beijing, Monday, Sept. 30, 2019. President Donald Trump said Thursday that he has not asked Xi to investigate the Biden family's business dealings, but that, "it's certainly something we could start thinking about." (Associated Press)

Hunter Biden was discharged from the Navy in February of 2014 after a positive drug test for cocaine in 2013, the Wall Street Journal reported at the time.

Biden, speaking recently to reporters in Iowa, had said he'd "never spoken to my son about his overseas business dealings." Fox News reported Tuesday, however, the former vice president appeared in a 2014 photo with Hunter Biden and Devon Archer, who served on the board of Burisma Holdings at the same time as Hunter. Biden allies maintain his intervention in Ukraine had to do with corruption concerns.

When asked by a reporter if he had spoken to President Xi about the Chinese opening an investigation into the Bidens, Trump said, "I haven’t but it’s certainly something we could start thinking about."

Later in his conversation with reporters, Trump speculated that there could be more countries in which Hunter Biden had allegedly illicit business activity.

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"I think Biden is going down," Trump said, "because now you may very well find that there are many other countries that they've scammed, just like they scammed China and Ukraine and basically who are they really scamming? The U.S.A and it's not good.

"And 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 like people with Biden where they give the son a billion-and-a-half dollars, and that's probably why China has such a sweetheart deal where for so many years they've been ripping off our country."

Fox News' Alex Pappas and the Associated Press contributed to this report.