President Donald Trump was to urge unity in his State of the Union speech Tuesday but the new spirit of bipartisanship risked withering before he even reached the podium.

The White House said the annual speech to Congress would see an "optimistic" Trump seeking to heal the Republican-Democratic divide.

"The president is calling for unity," senior advisor Kellyanne Conway told Fox News.

However, the president got into a testy exchange with the senior Democrat in the Senate, Chuck Schumer, just hours before he was due to give the nationally televised address from the chamber of the House of Representatives.

"The state of the Trump economy is failing America's middle class," Schumer tweeted.

"The state of the Trump healthcare system is failing American families. The state of the Trump Administration is chaos."

Trump ripped back at Schumer for "already criticizing my State of the Union speech, even though he hasn't seen it yet."

Another tough preview was due a few minutes before the speech when Democratic Senator Kamala Harris, who has announced a challenge to Trump in the 2020 presidential election, planned a so-called "prebuttal."

Once Trump finishes, the Democrats were to field another woman, Stacey Abrams, who almost upset the odds to win Georgia's governorship, to deliver the traditional rebuttal.

At the heart of the rancor is Trump's single-minded drive -- and failure -- to get congressional funding for walls along the US-Mexican border.

Trump says a wall or fence is needed to prevent an "invasion" of Central American migrants whom he repeatedly casts as a horde of killers and rapists.

In his latest tweet on the subject Tuesday, Trump again resorted to hyperbole, warning of "tremendous numbers" of illegal immigrants approaching, stating "we will build a Human Wall if necessary."

Democrats, who took control of the House of Representatives last year and therefore control half of Congress, accuse Trump of fearmongering and refuse to give their approval.

The resulting standoff has turned a relatively minor funding debate into an existential test of political strength in the buildup to 2020 presidential elections.

The row has seen an ever more frustrated Trump trigger a crippling five-week partial shutdown of government in revenge.

Democratic House speaker Nancy Pelosi, who will be sitting a few feet behind Trump during the State of the Union, exacted her own reprisal by forcing the speech to be delayed by a week.

Things could soon escalate, with Trump threatening to declare a national emergency so that he can bypass Congress and give himself power to take military funds for his project.

Officials say the speech will tout the strength of the US economy, a key element in Trump's 2020 reelection hopes.

The White House says he will also propose federal infrastructure spending, an area where Democrats could conceivably join forces with the government.

More contentiously, Trump will claim foreign policy successes.

That means defending his push -- criticized by some in the security services and many in his own Republican Party -- to withdraw US soldiers from Syria and Afghanistan as soon as possible.

Trump is likewise expected to update Congress on China trade talks and on his intention to hold a second summit with reclusive North Korean leader Kim Jong Un, whom he is trying to persuade to give up nuclear weapons.

Closer to home, he will likely dial up the pressure on Venezuela's leftist leader Nicolas Maduro. Opposition leader Juan Guaido's envoy to Washington is among the top guests invited to attend the speech.

Among those watching Trump from the chamber will be members of Democrat-chaired House investigative committees determined to probe the president's personal finances and other sensitive areas.

That's on top of the huge investigation by special prosecutor Robert Mueller, who is charged with examining alleged collusion between the Trump election campaign and the Kremlin.

New trouble emerged late Monday with reports that New York federal prosecutors have issued subpoenas in a sweeping probe of suspected fraud and other crimes by Trump's lavish 2016 presidential inauguration committee.

"This has nothing to do with the White House," Trump spokeswoman Sarah Sanders told CNN in an attempt to distance the president from the latest scandal.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)