Democratic presidential candidate Joe Biden has delivered a withering assessment of Donald Trump’s four years in office, vowing to heal a country battered by a deadly pandemic and an economic catastrophe by uniting all Americans

“Here and now, I give you my word: if you entrust me with the presidency, I’ll draw on the best of us, not the worst,” Mr Biden said as he accepted the Democratic presidential nomination for an election 75 days away.

“I’ll be an ally of the light, not the darkness.”

Mr Biden warned President Donald Trump would go on stoking hatred and fear if elected to another four-year term.

The speech was delivered inside an empty arena in his hometown of Wilmington, Delaware, at the conclusion of the four-day Democratic National Convention, which was held virtually because of the coronavirus pandemic.

The former US senator and vice president described the current moment as one of historical import, amid a health crisis over the coronavirus, a recession, a national reckoning on race and a battle over the environment.

He promised to represent all Americans and to work “just as hard” for those who do not support him, drawing an implicit contrast with the Republican Mr Trump.

“Our current president has failed in his most basic duty to the nation: he has failed to protect us,” Biden said.

Several Democrats who challenged Mr Biden for the nomination – US Senators Bernie Sanders, Elizabeth Warren, Amy Klobuchar and Cory Booker; former US Representative Beto O’Rourke; and entrepreneur Andrew Yang – praised Mr Biden’s empathy and leadership in a taped conversation.

As they have throughout the week, Democrats emphasised the importance of voting amid the pandemic and warned against efforts to suppress the vote. Trump’s repeated, unsubstantiated claims that mail-in ballots are rife with fraud, coupled with cuts to the US Postal Service, have fuelled fears that some voters may be disenfranchised.

The program offered some light-hearted moments from its moderator, Julia Louis-Dreyfus, who portrayed a US vice president in the comedy television show “Veep”.

“When Donald Trump spoke at his inauguration about ‘American carnage,’ I assumed that was something he was against, not a campaign promise,” she said.

The day offered new fodder for the Biden campaign to highlight what convention speaker after speaker has characterised as Mr Trump’s chaotic four years in office.

Steve Bannon, an architect of Trump’s 2016 election victory, was arrested on fraud charges, while in New York a judge ruled Trump cannot block a prosecutor’s subpoena for eight years of his tax returns.

Mr Biden, 77, heads into the general election campaign leading in opinion polls over Trump, 74, who will accept the Republican nomination for a second White House term at his own convention next week.

More than 70 Republican former national security officials, including former heads of the FBI and CIA, plan to endorse Biden on Friday while calling Trump unfit to serve.

Mr Trump has campaigned across the country to offer counter-programming to the Democrats, a break with tradition in which candidates limit their activities during their opponents’ conventions.

The President held a campaign event on Thursday near Biden’s birthplace of Scranton in the battleground state of Pennsylvania, where he slammed his Democratic challenger’s long record in government.

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Mr Biden, who became a US senator from Delaware in 1973 before becoming Obama’s vice president, captured the nomination by convincing Democratic primary voters he was the best bet to beat Mr Trump.

-with agencies