Former Vice President Joe Biden Joe BidenMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE in an interview on Thursday said he regrets not being president.

"I have a regret that I am not president, because I think there is so much opportunity," Biden told Oprah Winfrey in a clip from "Super Soul Sunday" on the Oprah Winfrey Network (OWN) which airs on Sunday.

Biden went on to explain why he did not launch a presidential bid in 2016, despite saying he believed he was the most qualified person for the job.

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"Was I prepared to give my whole heart, my whole soul, and my whole attention to the endeavor?" he said, adding, "I know I wasn't."

Biden has said his decision not to run in 2016 was related to the death of his son Beau Biden in 2015.

The former vice president has fueled speculation recently that he will launch a presidential run in 2020.

The political veteran launched his own super PAC, and has taken part in a slew of public appearances in which he has been critical of former Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE.

He is now in the process of promoting his new memoir, "Promise Me, Dad."

Biden refused to rule out a future run in an interview on Tuesday with The Salt Lake Tribune, saying, "The honest-to-God answer is that I don’t know.”

- This post was updated to clarify where Biden made his comments.