Standing before a Congress and nation sharply divided by impeachment, US President Donald Trump used his State of the Union address on Tuesday to extol a “Great American Comeback” on his watch, just three years after he took office decrying a land of “American carnage” under his predecessor.

The partisan discord was on vivid display as the first president to campaign for reelection while facing impeachment made his case for another term: Republican legislators chanted “Four More Years” while House Speaker Nancy Pelosi ripped up her copy of Trump’s speech as he ended his address.

Facing a Democratic party stumbling from divisions and a chaotic start to the primaries, Trump strode confidently to the podium in the House of Representatives, where just last December he was impeached for abuse of office.

And he laid down an immediate marker that he was in campaign mode — with little intention of placating opponents — when he broke with custom by not shaking hands with the Democratic speaker of the House, Nancy Pelosi.

Democrats repaid the favour throughout the speech by remaining in their seats, often in silence, while Republicans leapt up for standing ovation after ovation.

The sight perfectly captured the polarisation gripping the country ahead of November's elections.

“America’s enemies are on the run, America’s fortunes are on the rise and America’s future is blazing bright,” Trump declared. “In just three short years, we have shattered the mentality of American decline and we have rejected the downsizing of America’s destiny. We are moving forward at a pace that was unimaginable just a short time ago, and we are never going back.”

Holding out the nation’s economic success as the chief rationale for a second term, Trump’s speech resembled a lower-volume version of his campaign rallies, providing something for every section of his political base.

"Unlike so many who came before me, I keep my promises," he said in the prepared remarks.

No impeachment mention

This could have been the darkest week of Trump's administration, with only the third presidential impeachment trial in US history poised to culminate on Wednesday with the Senate delivering a verdict.

Trump has for months fulminated against what he calls a "witch hunt" and stonewalling investigators.

Facing him during the speech was a sea of hostile Democratic legislators, several of them booing during Republican applause — a rare gesture in what has traditionally been an annual moment for political truce.

Pelosi, sitting just behind Trump, also frowned and sometimes smiled disbelievingly at the president's claims.

But while Democrats control the House, Trump's Republicans hold a majority in the Senate and they were all but sure to declare him not guilty of both impeachment charges less than 24 hours after he finished speaking.

Ignoring the entire drama, Trump did not pronounce the word "impeachment" once in the prepared text of the 20-page speech.

Trump himself told TV network anchors at an annual lunch hosted by the White House before the speech that he'd be "extraordinarily low-key" and wasn't feeling "bitter" at all, Politico reported.

Battle of the guests

Trump had already spent the earlier part of Tuesday mocking the Democrats' shambolic kick-off to their primary season, saying that delays in the vote count in Iowa proved their incompetence.

“Nothing works, just like they ran the country,” Trump said on Twitter.

Reflecting the bitter atmosphere in the country ahead of the November presidential elections, prominent young leftwing lawmakers Alexandria Ocasio-Cortez and Ayanna Pressley were among several Democrats declaring they'd boycott the State of the Union.

"I will not use my presence at a state ceremony to normalise Trump's lawless conduct & subversion of the Constitution," Ocasio-Cortez tweeted.

The choices of guests to the big event told their own stories as the election campaign picks up.

Trump invited a senior border patrol officer, a woman whose brother was murdered by an illegal immigrant in 2018, and former Caracas police chief Ivan Simonovis who spent years in jail under Venezuela's far-left government.

And Venezuelan opposition leader Juan Guaido, recognized as the country's interim president by the United States, was also a guest in a public show of support by Trump for his efforts to dislodge President Nicolas Maduro.

Democratic party leaders' guests included some 80 doctors, patients and others symbolizing what they say is the Trump administration's failure to tackle health care problems.

Trump got yet more good news on Tuesday with a Gallup poll showing his approval rating at its highest ever: 49 per cent.

Support was up both among Republicans and independents, though opposition among Democrats had deepened more than ever, the poll found.