US first lady Melania Trump urged voters to re-elect her husband during an impassioned speech to the Republican National Convention on Tuesday that offered sympathy for victims of the coronavirus pandemic and a plea for racial understanding.

On the second day of the convention with 70 days to go until the November 3 election, the speech's warm tone was out of step with a Republican gathering that featured harsh rhetoric about Democratic challenger Joe Biden and sometimes apocalyptic warnings about the dangers of Democratic governance.

“I don't want to use this precious time attacking the other side because, as we saw last week, that kind of talk only serves to divide the country further,” Melania told a crowd seated in the White House's Rose Garden, including her husband, US President Donald Trump, in the front row.

In a speech aimed at disaffected suburban women voters who have abandoned Trump, the first lady acknowledged the pain of the coronavirus pandemic in a way few other speakers at the Republican convention have.

“Donald will not rest until he has done all he can to take care of everyone impacted by this terrible pandemic,” she said. “My deepest sympathy goes out to everyone who has lost a loved one.”

She also reflected on the racial unrest that has swept the country in the months since the death in May of George Floyd under the knee of a white policeman in Minnesota.

“I also ask people to stop the violence and looting being done in the name of justice, and never make assumptions based on the colour of a person's skin,” she said.

The speech by the first lady, whose 2016 convention speech was marred by plagiarism of lines from Michelle Obama's 2008 convention speech, capped a day when Republicans sought to reshape the narrative around the economy by largely ignoring millions of jobs lost to the coronavirus pandemic, which has cost more than 177,000 Americans their lives.

It was a case of emphasising a strength for Trump, who still scores well in opinion polls on his handling of the economy even as approval of his handling of the pandemic and other issues has plunged.

A former reality television star, Trump, 74, used videos of a naturalisation ceremony and signing a pardon to suggest that he is not anti-immigrant or a hardliner on crime — even as the convention has emphasised his law-and-order approach.

An array of officials and everyday Americans cited Trump's efforts to loosen economic regulations, put “America First” in trade deals and support religious freedom as reasons to back him against Biden, 77, and Barack Obama's former vice president.

“Our economic choice is very clear. Do you want economic health, prosperity, opportunity and optimism, or do you want to turn back to the dark days of stagnation, recession and pessimism?” White House economic adviser Larry Kudlow said.

Dire portrait

Before Melania's speech, the tone at times echoed Monday's opening day, when Republicans reached out to their conservative core supporters by painting a dire portrait of a future America under Biden's leadership.

Cissie Graham Lynch, granddaughter of the late evangelist Reverend Billy Graham, said a Biden presidency would leave “no room for people of faith”.

Biden is Catholic, and his faith was highlighted at last week's Democratic convention where he was formally nominated.

Pete Buttigieg, a Democratic former Indiana mayor who ran for president before endorsing Biden, challenged that characterisation on Twitter, recalling a walk Trump took to a nearby church during protests outside the White House to hold up a Bible for photographers.

“They would speak of faith? The choice here is so simple. One man waves a borrowed Bible around, the other actually reads it,” Buttigieg tweeted.

In an appeal to Black voters, many of whom have been alienated by his sometimes divisive rhetoric, Trump in a video issued a pardon to a convicted Nevada bank robber, Jon Ponder, a Black man who has become an advocate for other inmates.

Trump, assailed by rights activists for immigration policies that have included separating families at the southern border with Mexico, also appeared in a video leading a naturalisation ceremony for five immigrants becoming US citizens.

US State Secretary Mike Pompeo, speaking from a Jerusalem rooftop with the city lights visible in the background, praised a recent deal to normalise relations between Israel and the United Arab Emirates.

Pompeo, believed to be weighing a 2024 run for the White House, also highlighted the 2018 move of the US Embassy to Jerusalem, which was popular with American evangelicals — a critical part of Trump's core support.

'Bold initiatives'

Another person who had been expected to speak to the convention was Mary Ann Mendoza, whose police officer son died in a head-on collision with a drunk driver who was in the country illegally.

The Trump campaign said she was pulled from the programme after tweeting a link to an anti-Semitic conspiracy theory. She later apologised.

US Senator Rand Paul of Kentucky reminded voters that Biden had voted to authorise the invasion of Iraq when he served in the US Senate.

“I fear Biden will choose war again. He supported war in Serbia, Syria and Libya. Joe Biden will continue to spill our blood and treasure. President Trump will bring our heroes home,” Paul said.

Melania's remarks and the speech by Pompeo, from a diplomatic trip to Israel, were criticised by Democrats who questioned the propriety of using the presidential residence for political purposes and of Pompeo making a political speech while on a government trip.

Trump himself will deliver a speech from the White House lawn on Thursday.

A total of 17 million people watched the Republican convention's first night on Monday, according to Nielsen, fewer than the 19.7 million TV viewers who watched the first night of the Democratic National Convention last week.