Former US President Obama said many leaders did not know what they were doing when referring to Covid-19 in a public speech.

"This pandemic has torn the curtain that many leaders know what they are doing. Many of them don't even pretend to be running," former US President Barack Obama told the delegates.

Obama did not directly mention US President Donald Trump, but his message was implicitly a criticism of the White House boss's Covid-19 approach.

Former President Obama also emphasized the epidemic that showed ethnic inequality in the United States, and expressed anger at the 25-year-old black man Ahmaud Arbery was shot dead while jogging in Georgia state on 23 /

"We see the disproportionate influence of Covid-19 on the communities. A black man jogged and some felt empowered to interrogate him, then shot to kill just for him.

Obama in early May called the White House's Covid-19 response a "disaster".

Covid-19 has appeared in more than 210 countries and territories, causing more than 4.7 million people to be infected and more than 312,000 people to die.