Washington DC - A newly published recording of former US President Joe Biden speaking hesitantly and struggling to remember key events and dates has fueled renewed debate over his mental capabilities while still in office.

The four-minute audio clip, obtained by news outlet Axios and published Saturday, coincides with the upcoming release of a book that alleges White House staff covered up Biden's decline even as he was seeking reelection.

The clip was taken from two October 2023 interviews with former special counsel Robert Hur, who was investigating whether Biden had criminally mishandled public records after leaving office as vice president to Barack Obama.

Questions about Biden's physical and cognitive abilities -- and the responses of staff and key Democrats to evident signs of decline – have flared with Tuesday's release of Original Sin: President Biden's Decline, Its Cover-Up, and His Disastrous Choice to Run Again by CNN journalist Jake Tapper and Alex Thompson of Axios.

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When the special counsel released his findings in a voluminous report, describing Biden as a "sympathetic, well-meaning, elderly man with a poor memory," it drew fury from Democrats and White House officials.

But the audio hints at the extent of his confusion and underscores Biden's seemingly tenuous grip on dates.

Describing the impact of the death from brain cancer of his son Beau, Biden struggles to remember exactly when it happened.

"What month did Beau die?" he asks in a soft voice. "Oh God, May? Was it 2015 he died? I think it was 2015."

He goes on to say, "And Trump gets elected in November of 2017," before being corrected and saying, "That's when Trump gets sworn in."

His delivery is slow and halting, including lengthy pauses and occasional shifts in topic mid-sentence.

The former president comes across as having been shattered by his son's death. "Beau was like my right arm," he says. And "Beau knew how much I adored him."

Biden later lashed out at Hur for bringing up his son's death, saying, "I don't need anyone to remind me when he passed away."

Biden spokesperson Kelly Scully told CNN that "the transcripts were released by the Biden administration more than a year ago. The audio does nothing but confirm what is already public."

Republicans had called for the release of the recording, but the Biden administration refused, citing executive privilege.

Hur ultimately found that, while Biden had kept classified documents after leaving office, the evidence was insufficient to file charges – particularly as a jury would likely have been sympathetic to the "elderly man with a poor memory."

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Signs of Biden's evident decline – particularly his halting delivery and verbal stumbles – were on full display during his June 2024 presidential debate with Donald Trump.

The disastrous performance ultimately led to Biden stepping aside in favor of Vice President Kamala Harris, who lost to Trump following an abbreviated campaign.

78-year-old Trump, who himself has at times confused names and dates, has repeatedly described Biden as cognitively impaired.