Barack Obama describes Trump's handling of pandemic as a 'chaotic disaster'
In a leaked conference call with former members of his administration, the ex-president said: "What we're fighting against is these long-term trends in which being selfish, being tribal, being divided, and seeing others as an enemy - that has become a stronger impulse in American life."
Mr Obama said that the world's response to the COVID-19 outbreak had been "anaemic and spotty".
Although he said the fallout from coronavirus in the US would have been bad "even with the best of governments", he added: "It has been an absolute chaotic disaster when that mindset - of 'what's in it for me' and 'to heck with everybody else' - when that mindset is operationalised in our government."
The former president also vowed he will be "campaigning as hard as I can for Joe Biden" ahead of November's election.
With more than 75,000 deaths, the US has had more fatalities from COVID-19 than any other country. Almost 1.3 million people have been infected there so far.
Mr Obama has made few public comments about America's response to the pandemic, even as Mr Trump accused his administration of failing to stockpile supplies.
White House spokeswoman Kayleigh McEnany has described Mr Trump's handling of the coronavirus as "unprecedented" - and claimed the president's actions have helped save American lives.
"While Democrats were pursuing a sham witch hunt against President Trump, President Trump was shutting down travel from China. While Democrats encouraged mass gatherings, President Trump was deploying PPE, ventilators, and testing across the country," she said.
Polls suggest that the race between Donald Trump and Joe Biden is tight, with just six months to go until Americans cast their vote.