President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE took aim at former special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE and Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE late Thursday, renewing his criticism of the former vice president's age while suggesting that Mueller's appearance before House lawmakers on Wednesday made Biden look like a "dynamo."

“Sleepy Joe is OK, but he’s fading; I think he’s fading fast," Trump said of Biden's 2020 presidential campaign in an interview with Fox News's Sean Hannity Sean Patrick HannityFormer Florida attorney general calls Kyle Rittenhouse 'a little boy out there trying to protect his community' Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Cruz: Trump should nominate a Supreme Court justice next week MORE. "The only good thing about Mueller is that it made Joe Biden look like a dynamo.”

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Trump's remarks came in his first interview since Mueller appeared before the House Judiciary and House Intelligence committees to testify on his more than 400-page report, which detailed his investigation into Russia's election interference and possible obstruction of justice by Trump.

Mueller's performance in his back-to-back hearings drew widespread criticism among those who questioned his grasp of his own investigation.

While many Democrats publicly praised his testimony before the House panels, some privately expressed a sense of disappointment in Mueller's at times shaky performance.

Trump has repeatedly attacked Mueller's investigation as a "witch hunt" and sought to cast doubt on the report's findings. Mueller did not charge Trump with obstruction, but has asserted repeatedly that the president was not exonerated by his investigation.

Trump, meanwhile, has sought to undermine Biden's endurance as a top-tier presidential contender, casting the former vice president as "sleepy."

The president on Thursday also went after other leading presidential contenders, including Sens. Elizabeth Warren Elizabeth WarrenHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Democratic senators ask inspector general to investigate IRS use of location tracking service MORE (D-Mass.) and Bernie Sanders Bernie SandersThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Bernie Sanders: 'This is an election between Donald Trump and democracy' The Hill's 12:30 Report: Trump stokes fears over November election outcome MORE (I-Vt.).

“You have Elizabeth Warren, formerly known as Pocahontas — and I’m sure that’ll come out because that’s a tough thing for her to withstand, I believe, because her whole life is a fake,” he said, referring to her past claims to Native American ancestry.

“Bernie looks like to me like he’s fading,” he added of the 77-year-old Vermont senator, before saying that Sanders gave up his chance to win the Democratic Party's presidential nomination after losing to then-candidate Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE in 2016.