Vowing to "put everything into this", President Barack Obama has unveiled the most sweeping proposals in 20 years to tighten gun control in the United States, including universal background checks on anyone trying to buy a gun, and a renewed ban on assault weapons, coupled with a 10-round limit for magazines.

At the same time - 33 days after the school shootings in Connecticut that horrified the nation - he signed 23 presidential executive orders that will speed up access to data on gun-purchasers, provide more money for mental health and funnel extra resources to police.

"These are concrete steps we can take right now, a specific set of proposals," Obama said, flanked by children who had written to him since the Newtown massacre, in which 20 children aged under 8 and six teachers were killed.

But despite the widening clamour for action, and tough measures at state level, a ferocious, and perhaps unwinnable, battle lies ahead in Congress, which must pass the laws on background checks and assault rifles.

Even before Obama spoke, the National Rifle Association declared: "These gun control schemes have failed in the past and will have no impact on public safety and crime."

More provocatively still, it put out a cable TV and internet advert referring directly to Obama's two school-age daughters.

"Are the President's kids more important than yours?" a narrator says. "Then why is he sceptical about putting armed security in our schools when his kids are protected by armed guards at their schools?"

The ad described the President (whose children attend private school in Washington DC and have Secret Service protection) as "just another elitist hypocrite". An Obama spokesman called the advert "repugnant and cowardly".

Within minutes of Obama's speech, some Republican-run states were announcing they were looking into ways of blocking some of the decisions announced by executive order. But the biggest problem on Capitol Hill may not be Republicans, whose hostility is taken for granted by the White House - but members of the President's own party, especially Democrats from conservative states with a strong gun tradition.

Nevada's Harry Reid, the Senate majority leader and the most powerful Democrat in Congress, has made it clear an assault weapons ban has virtually no chance of passage.

But Obama is gambling he can shame Congress by carrying the battle to the country, where public opinion has shifted notably in favour of tighter controls since the Connecticut shootings and a spate of other deadly incidents.

Boosting him have been polls showing clear support, including one by CNN yesterday showing a 55-45 majority in favour of tougher gun controls. A lopsided 84 per cent in a new AP-GfK poll backed wider background checks, and nearly 60 per cent want stricter gun laws. New York measures signed into law this week by Governor Andrew Cuomo go even further than Obama's.

The President repeatedly used the words "common sense" for his proposals. America was the land of the free and would remain so, he said, adding: "I respect the Second Amendment and the rights of gun-owners."

Most gun-owners, he said, accepted that respect for that constitutional right did not rule out steps to prevent guns "doing harm on a massive scale". He acknowledged that some gun advocates would brand his scheme the precursor of a government attempt to outlaw guns completely - a fear borne out by a surge in NRA membership since Newtown, and a run on assault weapons.

Such arms, used by the Connecticut gunman Adam Lanza and in the July 2012 cinema shooting in Aurora, Colorado, in which 12 people died and 58 others were wounded, were outlawed by Congress in 1994, when President Bill Clinton was in the White House. But George W. Bush made no attempt to extend the ban when it expired in 2004.

Above all, Obama stressed, speed was of the essence - when the country was still outraged at the Newtown killings, and while his own power was at its zenith, reinforced by election victory in November.

"I will put everything into this, I will use every power of this office. If there is even one thing we can do, even one life we can save, we've got an obligation to try it."

New gun control steps

Needs congressional action:

•Requiring background checks on all gun sales. Forty per cent of gun sales are said to be conducted with no criminal background check, such as at gun shows and by private sellers using the internet or classified ads.

•Reinstating the assault weapons ban. A 10-year ban on high-grade, military-style weapons expired in 2004.

•Renewing a 10-round limit on the size of ammunition magazines.

•Prohibiting the possession, transfer, manufacture and import of armour-piercing bullets.

•Senate confirmation of a director for the Bureau of Alcohol, Tobacco, Firearms and Explosives. The agency has been run by an acting director, Todd Jones, whom Obama will nominate as director.

•New gun trafficking laws penalising people who help criminals get guns.

Dealt with by executive order:

•Address legal barriers in health laws that bar some states from making available information about people prohibited from having guns.

•Improve incentives for states to share information with the background check system.

•Make sure federal agencies share relevant information with the background check system.

•Direct the Attorney-General to work with other agencies to review existing laws to make sure they can identify individuals who shouldn't have access to guns.

•Direct the Centres for Disease Control and Prevention and other agencies to research the causes and prevention of gun violence.

•Clarify that no federal law prohibits doctors or other health providers from contacting authorities when patients threaten violence.

•Give communities the opportunity to hire up to 1000 school resource officers and counsellors.

•Require federal law enforcement to trace all recovered guns.

•Propose regulations to enable law enforcement to run complete background checks before returning seized firearms.

•Direct the Justice Department to analyse information on lost and stolen guns and make it available to law enforcement.

•Train state and local law enforcement, first responders and school officials on how to handle active-shooter situations.

•Make sure every school has a comprehensive emergency management plan.

•Help ensure that young people get mental health treatment.

•Ensure health insurance plans cover mental health benefits.

•Launch a national campaign on responsible gun ownership.

- Independent, AP