US first lady Michelle Obama waves as she stands between Connecticut Governor Dannel Malloy (L) and Vice President Biden's wife Dr. Jill Biden (R) as they attend US President Barack Obama's State of the Union address to a joint session of Congress in Washington, January 12, 2016. [Photo/Agencies]

In a swipe at some Republican presidential candidates, he warned against "voices urging us to fall back into tribes, to scapegoat fellow citizens who don't look like us or pray like us or vote like we do or share the same background."

South Carolina Governor Nikki Haley, who was selected to give the Republican response to Obama's address, underscored how the heated campaign rhetoric about immigrants and minorities from GOP front-runner Donald Trump in particular has unnerved some Republican leaders, Haley called on Americans to resist the temptation "to follow the siren call of the angriest voices".

Obama ticked through a retrospective of his domestic and foreign policy actions in office, including helping lead the economy back from the brink of depression, taking aggressive action on climate change and ending a Cold War freeze with Cuba.

Yet he was frank about one of his biggest regrets: failing to ease the persistently deep divisions between Democrats and Republicans.

"The rancor and suspicion between the parties has gotten worse instead of better," he conceded. "There's no doubt a president with the gifts of Lincoln or Roosevelt might have better bridged the divide, and I guarantee I'll keep trying to be better so long as I hold this office."

Obama avoided the traditional litany of policy proposals. He did reiterate his call for working with Republicans on criminal justice reform and also vowed to keep pushing for action on issues such as gun violence and fixing the nation's immigration laws.

Obama symbolically had a chair left empty in the box where First Lady Michelle Obama was sitting in honor of those who have died from gun violence. The hashtag #EmptySeat was trending heavily on Twitter in response to the gesture.

The single reference to "gun" compared with four mentions of "climate change" and 15 to the "economy."

Obama apparently has delivered on his promise to keep this year's speech shorter: The text of his speech unofficially comes in at 5,438 words versus 6,776 in his 2015 speech.

"The United States of America is the most powerful nation on earth. Period," Obama declared. "It's not even close."