US President Barack Obama has taken aim at Republican presidential front-runner Donald Trump and accused critics of playing into the hands of Islamic State in a speech meant to cement his legacy and set a positive tone for his final year in office.
Obama, delivering his last annual State of the Union speech to congress, called for leaders to "fix" US politics and criticised candidates such as Trump for using anti-Muslim rhetoric that betrayed American values.
"When politicians insult Muslims ... that doesn't make us safer," he said, drawing applause from the crowd in the House of Representatives chamber.
"It's just wrong. It diminishes us in the eyes of the world. It makes it harder to achieve our goals."
Trump, whom Obama did not mention by name in his speech, is leading the Republican field before the November 8 election of the next president.
The billionaire businessman, citing national security concerns, has called for a temporary ban on Muslims entering the United States and a wall on the US border with Mexico to stop the flow of illegal immigrants, ideas the White House strongly opposes.
Obama sought to contrast his more optimistic view of America's future with those of the Republican candidates trying to replace him.
He said it was "fiction" to describe the country as being in economic decline. While acknowledging that al Qaeda and Islamic State posed a direct threat to Americans, he said comparing the effort to defeat the militants who control swaths of Iraq and Syria to World War III gave the group just what it wanted.
"Masses of fighters on the back of pick-up trucks, twisted souls plotting in apartments or garages: they pose an enormous danger to civilians; they have to be stopped. But they do not threaten our national existence," Obama said.
Republicans say the president's strategy to defeat Islamic State is flawed and insufficient.
"His policies aren't working. He didn't have an answer for how to defeat ISIS," Republican House of Representatives Speaker Paul Ryan said in a statement after the speech. Trump, in a posting on Twitter, called the speech "boring" and lacking in substance. "New leadership fast!"
But South Carolina Governor Nikki Haley, who delivered the Republican response to Obama's address, took her own jab at Trump and other less moderate candidates in her party.
"During anxious times, it can be tempting to follow the siren call of the angriest voices. We must resist that temptation," said Haley, the daughter of Indian immigrants.
"No one who is willing to work hard, abide by our laws, and love our traditions should ever feel unwelcome in this country," she said.
Obama stuck to themes he hopes will define his legacy, including last year's nuclear pact with Tehran.
He noted areas where compromise was possible with Republicans in congress including criminal justice reform, trade and poverty reduction.
He called for lawmakers to ratify a Pacific trade pact, advance tighter gun laws and lift an embargo on Cuba.
The president also said he regretted not having been able to elevate US political discourse during his time in office.
"It's one of the few regrets of my presidency – that the rancour and suspicion between the parties has gotten worse instead of better," he said.
To help "fix" US politics, Obama pressed for an end to "gerrymandering", the practice of drawing voting districts in ways that gives advantage to a particular party, reducing the influence of "dark money" or political spending in which funding sources do not have to be disclosed and making voting easier.
Obama also said he had charged Vice President Joe Biden, whose son died last year of cancer, with leading an effort to find a cure for the disease.
"For the loved ones we've all lost, for the family we can still save, let's make America the country that cures cancer once and for all," Obama said.
As Biden smiled from his seat behind the president, Obama said he would put the vice president in charge of "mission control" for the effort.
Biden, who lost his 46-year-old son to brain cancer last year, received a standing ovation from legislators when Obama made the announcement.
Following his son's death, Biden said he would not run for president in 2016, but he promised he would focus his remaining time in office on working on a "moon shot" to end cancer.
In a blog post released during the State of the Union address, Biden said the White House would focus on increasing public and private resources to fight the disease and to improve information sharing among researchers and medical professionals.
"It's personal for me," Biden said, regarding the push.
He will travel on Friday (local time) to the University of Pennsylvania's Perelman School of Medicine to speak with physicians and next week he will meet with experts at the World Economic Forum in Davos, Switzerland to discuss the initiative.
The cancer initiative will build on the US$2 billion increase in funding approved for the National Institutes of Health last year, White House chief economist Jason Furman told reporters before the Obama speech.
The president noted some outstanding promises from his own 2008 campaign. He pledged to continue to work to close the US prison at Guantanamo Bay, Cuba, and called on congress to lift the embargo on the Communist-ruled island nation.
Obama, whose 2008 victory was driven partially by his opposition to the Iraq war, said the United States could not serve as policeman of the world.
"We also can't try to take over and rebuild every country that falls into crisis, even if it's done with the best of intentions," he said.
"It's the lesson of Vietnam; it's the lesson of Iraq; and we should have learned it by now."
AAP / Reuters