Washington (AFP) - Embattled US President Donald Trump delivers his biggest speech of the year Tuesday, a State of the Union address designed to sell his economic record to a fiercely divided America.

Trump's maiden State of the Union address -- last year, he technically only delivered a speech to Congress -- presents a once-in-a-year opportunity for the president to mend his sunken approval ratings.

As many as 40 million people are expected to tune in when Trump takes to the floor of the House of Representatives for an hour just after 9:00 pm (0200 GMT).

"It's a big speech, an important speech," Trump said Monday, offering a sneak peak of his remarks.

Over the years, the set piece event has lost some of its influence and Americans are increasingly tuning out shrill political discourse, but it can still mold and direct public debate for weeks to come.

In 94 previous addresses, presidents have described the state of the union as "good," "strong," "sound" or in the case of a glum Gerald Ford, "not good."

Expect no such moderation from the 71-year-old real estate mogul and reality TV star.

The state of the union is "incredible" said Sanders, outlining a speech that will be long on claims of achievement.

Trump is expected to tout a long bull run on Wall Street and improving growth rates, something the White House is calling a "Trump bump" and linking directly to the recent "Trump tax cut."

"We worked on it hard, covered a lot of territory," Trump said of the speech, "including our great success with the markets and with the tax cut."

Since Trump came to office a year ago, the Dow Jones Industrial Average is up by around 33 percent. The unemployment rate has reached a 17-year low.

At a recent address in Davos, Switzerland, Trump told the global great and good that "America is open for business" again.

During his first year in office, Trump has often sought credit, but he has appeared less concerned about widening his appeal -- defying norms and sticking to a base-first approach.

With legislative elections scheduled for November and the probe into his campaign's ties with Russia intensifying, Tuesday's speech may see something of a change in strategy.

"This is a president who wants to lead for everybody," said Sanders. "He's not looking to lead for any one person, any one group, but he wants to be the president of the United States."

Trump's approval rating is languishing around 40 percent, according to the RealClearPolitics average, and opposition is fierce.

At a donor retreat in the California desert this week, Republican strategists warned that an unpopular president and strong enthusiasm among Democrats could spell doom for the party.

But Trump's speech is also expected to touch on the highly charged issue of migration, where Trump continues to play firmly to his core supporters.

Two couples whose daughters were murdered by MS-13, a Salvadoran gang, are among those the White House invited to see the State of the Union address first hand.

His remarks are being crafted in part by aide Stephen Miller, who has for years been known in Washington as a hardliner on immigration and has been pressing for an uncompromising stance.

"For many years, for many, many years, they've been talking immigration, they never got anything done. We're going to get something done, we hope," Trump said.

"Hopefully, the Democrats will join us, or enough of them will join us, so we can really do something great."

- State of the world -

Trump can also be expected to lift his gaze beyond the United States to what Washington sees as Iran's troublesome activities across the Middle East, as well as North Korea's nuclear and ballistic missile programs.

Trade is also expected to be a strong focus, with Trump repeating claims that the current terms of global business are unfair to the world's largest economy.

"The world has taken advantage of us on trade for many years, and as you probably noticed we're stopping that, and we're stopping it cold," Trump said.

- The disloyal opposition -

Democrats' response will come in many forms, with Joe Kennedy offering the official rebuttals, but 2016 hopeful Bernie Sanders and a host of others offering their own take.

They are likely to concede that the economy is growing, but perhaps not for everyone.

"Trump inherited a years-long economic recovery but has yet to turn it to the advantage of working Americans," said analysts at the left-leaning Center for American Progress.

"The Trump administration's fiscal policies are redistributing income and wealth upward through massive new tax breaks to corporations and the wealthy, which come at the expense of middle-class and low-income Americans."

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