President Donald Trump was to deliver a triumphant State of the Union speech Tuesday on the eve of near certain acquittal in his impeachment trial, setting the stage for his re-election bid with a boast of "I keep my promises."

Facing a Democratic party smarting from divisions and a chaotic start to the primaries, Trump headed in buoyant mood to the House of Representatives, where just last December he was impeached for abuse of office.

"Three years ago, we launched the great American comeback. Tonight, I stand before you to share the incredible results," he said, according to excerpts released by the White House.

US President Donald Trump
US President Donald Trump spent last weekend relaxing in Florida, but the pressure is on. Photo: AFP / NICHOLAS KAMM

"We have shattered the mentality of American decline and we have rejected the downsizing of America's destiny."

Trump was to say that his policies of deregulation and tax cuts -- criticised by opponents as harming the environment and favoring the wealthy over the poor -- were responsible for "unparalleled success" in the economy.

In a note of togetherness to a deeply polarised nation, he was to insist that he is "building the world's most prosperous and inclusive society - one where every citizen can join in."

He listed the North American USMCA trade pact, a trade deal with China, massive military spending, "unprecedented" measures to stop illegal immigration, and his bid to "end America's wars in the Middle East" as examples of fulfilling his commitments to voters.

Trump impeachment trial
President Donald Trump's trial in the US Senate is unlikely to be the end of the scandal. Photo: US Senate TV / HO

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

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

US President Donald Trump
America's divisions will be on display at President Donald Trump's State of the Union speech. Photo: AFP / Nicholas Kamm

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

Facing him during the speech will be sea of hostile Democratic legislators. And just over his left shoulder will be House speaker Nancy Pelosi, whom Trump repeatedly insults in public, calling her "Nervous Nancy" and other nicknames.

But Trump's Republicans hold a majority in the Senate and they are all but sure to declare him not guilty of both impeachment charges, leaving the real estate tycoon and former TV personality in a triumphant mood.

The White House flagged well in advance that the speech would be "very optimistic."

The US Capitol
The US Capitol is the setting for the State of the Union speech every year. Photo: GETTY IMAGES NORTH AMERICA / CHIP SOMODEVILLA

The "I" word will not even be pronounced, the White House said.

"I read the speech and the word 'impeachment's' not in it," spokesman Hogan Gidley told Fox News shortly before the event.

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.

Of course with a president who loves to ad-lib and hates to play by the rules, he may yet launch a few verbal bombs at lawmakers.

He already spent 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 normalize Trump's lawless conduct & subversion of the Constitution," Ocasio-Cortez tweeted.

The choices of guests to the big event tell 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, will reportedly be a guest in a public show of support for his efforts to dislodge President Nicolas Maduro.

Democratic party leaders' guests will include 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 percent.

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

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