US President Donald Trump (C) attends a signing ceremony of the United States-Mexico-Canada Agreement (USMCA) at the White House in Washington D.C., the United States, on Jan. 29, 2020. U.S. President Donald Trump on Wednesday signed the revised United States-Mexico-Canada Agreement (USMCA) in an outdoor ceremony at the South Lawn of the White House. (Xinhua/Liu Jie)

The divisions of the US was expected to enter into burning focus on Tuesday when President Donald Trump delivers the annual State of the Union speech to Congress, just ahead of his expected acrimonious impeachment acquittal.

The State of the Union is a grand set-piece in the US political calendar, a rare occasion when bitter opponents traditionally observe a truce while the president lays out a vision for the future.

But Trump will drive up Pennsylvania Avenue to the Capitol at a time of rancor arguably unmatched for decades - and likely to worsen as the November presidential election approaches.

The White House promises Trump will be "relentless" in talking up the US economy and the "blue collar boom" when he takes to the podium at around 9:00 pm.

"I think the speech is going to have a very optimistic tone," a senior administration official told reporters.

The reality is that Trump will be entering a chamber where only last December the Democratic-led House of Representatives, the lower chamber, impeached him for abuse of power and obstructing Congress.

And he'll be looking out over a group of legislators where only a narrow Republican majority in the upper chamber Senate is likely to save his job when a verdict vote comes Wednesday.

The speech could in theory be an opportunity to reach out and heal a nation boiling over in mistrust.

Trump could express regret for what even several of his own Republican senators agree was wrongful behavior in pushing Ukraine to open a questionable corruption probe against one of his main Democratic presidential opponents, Joe Biden.

Or he could seek to calm the waters by entirely avoiding the topic of impeachment, just as Bill Clinton did during his post-impeachment State of the Union in 1999.

White House officials say they don't know what he'll do.

"It's never safe to assume anything," the administration official said, when asked if impeachment will be kept out of the speech.

Republican senator, Roy Blunt, told The New York Times that Trump should "avoid" the "i" word.

"It's an opportunity to move on," Blunt said, while acknowledging that the real estate tycoon and reality TV show performer is not the type to turn down the volume. "The other option is to address it head on - and he is often a head-on kind of guy."

Right before the speech on Tuesday, the Senate was expected to be finishing up the impeachment trial. Closing arguments took place Monday.