In the last phone call between Biden and his Afghan then-counterpart Ashraf Ghani, the American president said they needed to shift the attention of the Taliban's rapid advance "whether it is true or not," according to citations published on Tuesday.
"The assumption was that more than 300,000 Afghan national security forces that we had trained over the past two decades, and equipped, would be a strong adversary in their civil wars with the Taliban," Biden told the country in a filmed speech from the White House on Tuesday.
"That assumption that the Afghan government would be able to hold on for a period of time beyond military drawdown turned out not to be accurate.
"But I still instructed our national security team to prepare for every eventuality, even that one. And that's what we did.
"So, we were ready when the Afghan security forces, after two decades of fighting for their country and losing thousands of their own, did not hold on as long as anyone expected."
Four weeks before Kabul collapsed, Ghani asked for more air support and money for veterans who had not had a pay increase in a decade.
A transcript received by Reuters from an anonymous source reveals two leaders unaware of the impending disaster and an American president adjusted on spinning the message.
"And there is a need, whether it is true or not, there is a need to project a different picture."
In the months leading up to the chaotic US military departure from Afghanistan, which was finished on Monday, Biden was telling the public another story - that the withdrawal would be done easily and that Washington's Afghan allies were in control.
"I don't think anybody anticipated that," Biden told ABC News when asked about the sudden disintegration of the Afghan security forces.