President Donald Trump said that former Vice President Joe Biden lied about whether or not he ever spoke to his son about his lucrative role on a Ukranian energy firm board.

“This is a very dishonest thing that Joe Biden did, and then he said he never spoke to his son,” Trump said. “Does anybody believe that one? But then he also said long before that he did speak to his son. So he lied again.”

The president spoke to reporters as he left the White House on Sunday for a visit to Houston, Texas, for a rally with Indian Prime Minister Narendra Modi.

The Trump campaign highlighted on Saturday Biden’s claim that he had “never” spoken to his son Hunter about his business interests overseas. Hunter, however, admitted in an interview in July that he spoke “just once” to his father about his business in Ukraine.

The president ripped Biden’s son Hunter for accepting a board position at the Ukrainian energy company Burisma Holdings, earning as much as $83,000 a month while his father was leading foreign relations with the country as vice president.

“The son, he knew nothing, the son is a stiff, he knew nothing,” Trump said. “And he’s making hundreds of thousands and millions of dollars, and he did the same thing in Ukraine, he knows nothing.”

Trump said that he “wasn’t looking to hurt Biden” despite possibly running against him for president but criticized Biden for threatening to cut aid from Ukraine if they did not fire a prosecutor who was investigating Burisma Holdings.

“He said a very foolish thing,” Trump said, referring to Biden.

Hunter Biden’s role with the Ukrainian energy firm and his deals with China were exposed in Peter Schweizer’s bestselling book Secret Empires.

In recent weeks, the establishment media has focused on Trump’s phone calls with the Ukrainian president, reportedly asking the government on multiple occasions to investigate Biden.

But Trump has insisted that his conversations with the Ukrainian president were not bad, even appearing willing to release the transcript.

“We had a very great conversation, very straight, very honest conversation,” he said. “I hope they can put it out.”