WASHINGTON, Jan 16, 2013 (AFP) - President Barack Obama Wednesday signed 23 executive actions to curb gun violence and demanded Congress pass an assault weapons ban, saying America cannot put off gun control measures "any longer."

Obama also called on Congress to pass deeper measures, including universal background checks for gun buyers and bans on high-capacity magazine clips and armor-piercing bullets, in response to the Newtown school massacre last month in which 20 small children and six adults were gunned down.

"Congress must act. Congress must act soon," Obama said, pledging to use the full weight of his office to pass new gun control measures.

"These are our children."

"What we should be thinking about is our responsibility to care for them and shield them from harm," Obama said, at an event at the White House, which included relatives of children killed at Sandy Hook Elementary school.

"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, he said, warning gun control reforms could not wait "any longer."

Most significant reforms in decades

The measures were drawn up in less than a month by Vice President Joe Biden, who praised the courage of relatives of gun crime victims from Newtown and elsewhere for showing up at the event.

Many of the most robust recommendations require Congress to pass new laws and skeptics believe the power of the US gun lobby and antipathy towards gun control among conservative Republicans and Democrats could limit action.

If enacted in full, Obama's package would represent the most significant gun control reforms in decades, but it is unclear whether they could have prevented tragedies like the one at Sandy Hook.

Specifically, Obama's executive orders would require government agencies to make relevant information available to 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 would provide training to schools on how to respond to an invasion by armed assailants.

The president also required the Centres 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.

In demanding action from Congress, arguing the single most important act in curbing gun crime would be to require background checks for all gun buyers, Obama also called on lawmakers to strengthen existing requirements.

Currently, licensed gun sellers are required to run background checks on customers, but private sales of firearms are exempt.

The president also urged Congress to renew a ban on assault weapons 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 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.

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 also nominated Todd Jones as the new director 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.

White House officials, while acknowledging the stiff political winds Obama's proposals will face, argue that the trauma of the Newtown killings on December 14 especially, may have changed political realities on the issue.

A new ABC News/Washington Post poll found most Americans support banning assault weapons and high-capacity ammunition magazines.

The poll found high support for some shifts: 88 percent favour background checks on buyers at gun shows; 76 percent urge checks on buyers of ammunition; 71 percent back the creation of a new federal database to track all gun sales; and 65 percent back banning high-capacity ammunition magazines.