Hunter Biden pointed to his experience on the board of Amtrak to justify his position on the board of a Ukrainian gas giant, despite not having "extensive knowledge" of natural gas or Ukraine.

In an interview that aired on Tuesday, he also admitted to ABC News anchor Amy Robach that he most likely would not have been on the board if he were not the son of Joe Biden, then the vice president of the United States.

"You didn't have any extensive knowledge about natural gas or Ukraine itself," Robach told Biden in an interview on Good Morning America.

"No, but I think I had as much knowledge as anyone else on that board, if not more," Biden said.

Robach also asked him what his qualifications were for the board of a natural gas company. Biden pointed to his time on the board of Amtrak, his position as chairman of the board of the U.N. World Food Programme, and his time at a prestigious law firm.

"In the list you gave me of the reasons why you're on that board, you did not list the fact that you're the son of the vice president," Robach said. "What role do you think that played?"

"I think that it is impossible for me to be on any of the boards I just mentioned without saying I'm the son of the vice president of the United States," Biden replied.

Robach asked Biden if he thinks he would have gotten any of these prestigious positions if his last name weren't Biden, and he said he wasn't sure.

"I don't know. Probably not. I don't think that there's a lot of things that would have happened in my life if my last name wasn't Biden," he said.

Biden's relationship with the Ukrainian firm Burisma Holdings has become the subject of controversy in the wake of a phone call between President Donald Trump and Ukrainian president Volodymyr Zelensky. The phone call, in which Trump is alleged to have withheld aid to Ukraine in order to pressure Zelensky to investigate potential corruption involving the Bidens, is the centerpiece of an impeachment inquiry.

Robach asked Biden how much his father, who is now running for president, knew about his activity in Ukraine.

"Well, he read the press reports that I'd joined the board of Burisma, which is a Ukrainian natural gas company," the younger Biden said. "And there's been a lot of misinformation—about me, not about my dad. Nobody buys this idea that I was unqualified to be on the board."