US President Donald Trump boasted on Tuesday of a "turnaround for the ages" in a State of the Union speech, seeking to reverse his dismal polls and see off mounting challenges at home and abroad ahead of crucial midterm elections.

Arriving to address a joint session of Congress, Trump was welcomed with cheers and a standing ovation from Republicans — while Democrats remained seated in protest.

"My fellow Americans, our nation is back bigger, better, richer and stronger than ever before," Trump said.

The 79-year-old hoped the prime-time stage would help him to sell voters on the achievements of a breakneck and deeply divisive first year back in power.

Trump is deep underwater in opinion polls and Republicans fear they could lose their tiny majority in the House to the Democrats — paralysing the rest of Trump's second term and exposing him to a possible third impeachment.

The Republican however struck a defiant tone in the first official State of the Union of his second term.

"Tonight, after just one year, I can say with dignity and pride that we have achieved a transformation like no one has ever seen before, and a turnaround for the ages," Trump said.

And he sought to seize on national enthusiasm over Team USA's gold medal winning Olympic ice hockey performance, inviting the players to join him on the floor of the Chamber to massive cheers and chants of "USA."

He then announced he was awarding the Presidential Medal of Freedom — the highest civilian honour — to the team's goalie.

The New York Times said at least 40 Democrats skipped the speech.

As US naval and air forces massed around Iran, Trump struck a tough posture.

There was intense scrutiny over whether Trump would use the speech to announce his next moves in Iran, where he has threatened to use force to crush the country's nuclear ambitions.

"As president, I will make peace wherever I can, but I will never hesitate to confront threats to America wherever we must," Trump said.

He also boasted that Venezuela, where US forces toppled long-time strongman Nicolas Maduro in January, was now shipping oil to the United States.

The annual speech to Congress is a rare chance to appear on all the major television networks simultaneously, and Trump is hoping to take advantage to shift the country's mood ahead of November's Midterms.

Trump has been battered by a series of blows in the second year of his second term, most recently with the Supreme Court's striking down of his trade tariffs policy.

Trump, who earlier branded the court's justices "fools and lapdogs" over the tariff ruling, briefly shook hands with several of the justices in attendance but went on in his speech to declare their ruling "very unfortunate."

He has also been rocked by a backlash by the killing of two US citizens in immigration raids in Minneapolis, the Jeffrey Epstein scandal, and a new partial government shutdown.

A Washington Post-ABC News-Ipsos poll published on Sunday showed his approval rating at 39 percent.

Only 41 percent approved of his handling of the economy overall, and just 32 percent on inflation. (AFP)


Edited by Thomas McAlinden