WASHINGTON: President Barack Obama on Wednesday demanded an assault weapons ban and universal background checks for gun buyers, stoking a generational clash with the firearms lobby after the Newtown school massacre.

“We can't put this off any longer. I will put everything I've got into this,” Obama said, laying out the most sweeping gun control legislation in decades and daring Congress not to defy public outrage and block his plans.

Obama signed 23 executive actions, using his presidential power in a swift effort to check a rash of gun violence including the killings of 20 kids at Sandy Hook Elementary School last month and other recent mass shootings.

And he challenged Congress to enshrine enduring reforms into law, including renewing and bolstering a ban on assault weapons, and closing loopholes that permit 40 per cent of gun sales to take place without background checks.

“This will be difficult,” Obama warned, unveiling measures drawn up by a task force led by Vice President Joe Biden at a White House event attended by gun crime victims, including the parents of a girl who perished in Newtown.

“There will be pundits and politicians and special interest lobbyists publicly warning of a tyrannical all-out assault on liberty,” Obama said.

“Behind the scenes, they'll do everything they can to block any commonsense reform and make sure nothing changes whatsoever,” Obama said, underlining he did not oppose the right to bear arms laid down in the US Constitution.

Immediate reaction from pro-gun politicians to Obama's plans to curb 11,000 annual firearms homicides in America hinted at the depth of that opposition.

“Guns require a finger to pull the trigger,” Texas Republican Governor Rick Perry said.

“The sad young man who did that in Newtown was clearly haunted by demons and no gun law could have saved the children in Sandy Hook Elementary from his terror.

“There is evil prowling in the world... let us all return to our places of worship and pray for help.”

Republican Senator Marco Rubio, a potential 2016 presidential hopeful, added: “guns are not the problem; criminals with evil in their hearts and mentally ill people prone to violence are.”

”President Obama is targeting the 2nd Amendment rights of law-abiding citizens instead of seriously addressing the real underlying causes of such violence.”

Obama appeared with four children, representing hundreds who wrote to him after the 20 children and six adults were killed when a gunman blazing an assault rifle went on the rampage in Connecticut last month.

“This is our first task as a society, keeping our children safe. This is how we will be judged and their voices should compel us to change.”

Specifically, Obama's executive orders would require government agencies to make relevant information available for background checks, and to examine new ways to prevent “dangerous” people getting guns.

Obama ordered a new national campaign on safe and responsible gun ownership, a review of safety standards for gun safes in the home, and new training to schools on how to respond to an invasion by armed assailants.

The president also required the Centers for Disease Control and Prevention to research the causes and prevention of gun violence, after some lawmakers tied the agency's hands in a bid to thwart new gun control measures.

Currently, licensed gun sellers are required to run background checks on customers, but private sales of firearms benefit from a loophole.

The president also urged Congress to renew a ban on assault weapons that expired in 2004 and to limit ammunition magazines to 10 rounds, in a bid to check the damage a shooter could do once engaged in a mass shooting.

The top gun lobby, the National Rifle Association (NRA), has expressed open skepticism about whether a renewed and strengthened assault weapons ban could get through Congress.

The NRA opposes most of the White House's likely proposals, and has instead called for armed guards at every US school.

The White House also complained Wednesday that an NRA attack ad accusing Obama of hypocrisy because his daughters get armed Secret Service protection and other school children do not was “repugnant and cowardly.”

Obama's package also seeks to crack down on guns trafficking, calling on lawmakers to equip law enforcement agencies with new powers to prosecute gun criminals.

He nominated acting director Todd Jones as the new head of the Bureau of Alcohol, Tobacco and Firearms, the top government regulatory body for firearms.

The agency has been without a director for six years after Republicans refused to allow Senate confirmation after successive nominees fell prey to heavy opposition from gun rights groups.

Biden arrived at his recommendations after several weeks of meetings with gun crime victims, pro-gun control groups, firearms lobby officials, mental health advocates and makers of video games which include violent content.