Former first lady Michelle Obama launched a scathing attack on President Donald Trump on the first night of the Democratic National Convention on Monday, calling him the "wrong president" for the country and urging Americans to elect Joe Biden in November to end the chaos created by Trump's presidency.

While acknowledging she did not care much for politics, Obama said Biden's steady and empathetic approach to problems was the answer and urged voters to stand in line or do whatever it takes to ensure they can beat Trump.

"Whenever we look to this White House for some leadership or consolation or any semblance of steadiness, what we get instead is chaos, division, and a total and utter lack of empathy," Obama said, adding Trump was "in over his head" as president.

"So if you take one thing from my words tonight, it is this: if you think things cannot possibly get worse, trust me, they can; and they will if we don’t make a change in this election. If we have any hope of ending this chaos, we have got to vote for Joe Biden like our lives depend on it."

Obama, whose husband Barack Obama was president when Biden was vice president from 2009-2017, capped a long parade of speakers, including some of Trump's fellow Republicans, who made the case for Biden at the start of his four-day nominating convention.

Former rival Bernie Sanders and prominent Republican John Kasich said Biden's steady approach to problems was needed to confront the coronavirus pandemic, economic woes and racial injustice.

"Joe Biden will end the hate and division Trump has created. He will stop the demonization of immigrants, the coddling of white nationalists, the racist dog whistling, the religious bigotry and the ugly attacks on women," said Sanders, a US senator and Biden's top primary rival.

The coronavirus pandemic forced Biden's Democrats to overhaul the convention, largely eliminating the in-person gathering planned for Milwaukee, Wisconsin, and turning it into two-hour, prime-time packages of virtual speeches and events from around the country.

The convention featured discussions with voters who described their struggles confronting the virus and coping with the slumping economy and healthcare.

Kristin Urquiza, who lost her father to COVID-19, blamed Trump's mismanagement of the pandemic for his death.

"My dad was a healthy 65-year-old. His only pre-existing condition was trusting Donald Trump, and for that, he paid with his life," she said. "When I cast my vote for Joe Biden, I will do it for my Dad."

The convention opened amid widespread worries about the safety of voting in November because of the coronavirus pandemic. Democrats have pushed mail-in ballots as a safe alternative, but fear it could be hindered by cost cuts at the Postal Service that, under Louis DeJoy, a top Trump donor, have led to delays in mail service.

"The president may hate the Post Office, but he's still going to have to send them a change of address card come January," said US Senator Amy Klobuchar, who ran unsuccessfully against Biden in the 2020 primary.

The convention also highlighted a call for a broad racial reckoning over systemic racism and police brutality amid protests that broke out after the death of African American George Floyd in Minnesota under the knee of a white policeman.

Speaking from Houston, Floyd's brother Philonise Floyd introduced a moment of silence and honored other Black victims of police violence.

"So, it's up to us to carry on the fight for justice. Our actions will be their legacies," Floyd said.

A video showed Biden speaking virtually with activists and officials around the country about ways to battle racism.

Jim Clyburn, the influential US Representative from South Carolina whose endorsement of Biden was critical to his breakthrough primary victory in that state in February, said Biden understood the need to unify people was part of presidential leadership.

Kasich, a former Ohio governor and frequent Trump critic who lost to Trump in the 2016 Republican primary, described his opposition to Trump as a patriotic duty and said the country was at a crossroads.

Standing literally at a fork in a road, he called Biden "a man who can help us see the humanity in each other."

Speaking to reporters on Air Force One, Trump said Kasich "was a loser as a Republican and he'll be a loser as a Democrat."

Other Republicans on the speakers list included former New Jersey Governor Christine Todd Whitman and former Hewlett Packard Enterprise Chief Executive Meg Whitman.

"Donald Trump has no clue how to run a business, let alone an economy. Joe Biden, on the other hand has a plan that will strengthen our economy for working people and small business owners," Meg Whitman said.

The inclusion of Republican speakers angered some Democrats who voiced concern it would take time away from progressive speakers like Sanders of Vermont and US Representative Alexandria Ocasio-Cortez.

But Cedric Richmond, a Louisiana congressman and Biden campaign co-chair, pushed back against that idea, telling reporters earlier in the day, "Remember tonight's theme is 'We the People,' not 'We the Democrats.'"

In a break with tradition, Trump looked to steal Biden's spotlight by crisscrossing the United States in a campaign swing to Wisconsin and Minnesota. Candidates usually limit their activities during their opponents' convention week.

Biden, 77, leads Trump, 74, in national opinion polls heading into back-to-back convention weeks for the two political parties. Trump will be formally nominated for a second term at next week's Republican National Convention, which also has been scaled back due to coronavirus concerns.