Former U.S. President Barack Obama described President Donald Trump's handling of the coronavirus pandemic as "chaotic" in a conference call with former members of his administration, a source said on Saturday.

In his call on Friday with 3,000 members of the Obama Alumni Association, people who served in his administration, Obama urged his supporters to get behind Democratic presidential candidate Joe Biden, who is trying to unseat Trump in the November 3 election, Reuters reported.

National polls show a tight race between Trump and Biden with six months to go until the election. Biden leads in several battleground states.

Read more:

Biden scores 3 big wins as COVID-19 hits Democratic primaries

Obama said the election "is so important because what we're going to be battling is not just a particular individual or a political party." 

"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," he said.

He said this is one reason why "the response to this global crisis has been so anemic and spotty." 

"It would have been bad even with the best of governments. 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 operationalized in our government," Obama said. 

"That's why, I, by the way, am going to be spending as much time as necessary and campaigning as hard as I can for Joe Biden," he said. "I am hoping that all of you feel the same sense of urgency that I do."

After formally endorsing Biden last month, Obama said he would be deeply involved in the campaign to help Biden win the White House. Obama is the latest high-profile Democrat to endorse Biden after fellow contestants Bernie Sanders and Michael Bloomberg.

Obama's office declined to comment.

Read more:

Obama says Biden can 'heal' U.S. in dark times as he endorses ex-vice president

White House press secretary Kayleigh McEnany on Saturday dismissed the criticism from Obama, saying in a statement to CNN: "President Trump's coronavirus response has been unprecedented and saved American lives."

Weighing in on the Department of Justice's decision to drop charges against Michael Flynn during the call, Obama said Attorney General William Barr's decision suggested "the rule of law was at risk" in the United States. Before taking office, Obama warned Trump about Flynn and raised questions about his conduct with Russia.

The White House did not respond to Obama's comments.