WASHINGTON (AP) — President Barack Obama is launching the most sweeping effort to curb U.S. gun violence in nearly two decades, acting swiftly after last month’s Connecticut school shooting with proposals to ban military-style assault weapons, high-capacity ammunition clips and more than a dozen executive orders aimed at circumventing congressional opposition to stricter gun control.

Families of the victims of last month’s shooting have been invited to the White House for the president’s announcement, which promises to set up a bitter fight with a powerful pro-gun lobby that has long warned supporters that Obama wanted to take away their guns.

The U.S. has the highest rate of gun ownership of any country in the world, and pro-gun groups see any move on gun restrictions as an offense against the cherished right protected by the Second Amendment of the U.S. Constitution. Critics counter that the country’s founding fathers never could have foreseen assault weapons more than two centuries ago, when guns were intended for the common, not individual, defense, guns were often stored in community areas and rifles fired one shot at a time.

Emotions have been high since the Connecticut shooting, which Obama has called the worst day of his presidency. He has moved quickly on an issue he largely ignored during his first term but appears willing to stake his second term on it now.

The general appears receptive to stronger federal action, with majorities of Americans favoring a nationwide ban on military-style rapid-fire weapons, according to a new Associated Press-GfK poll. The poll shows 84 percent of adults would like to see the establishment of a federal standard for background checks for people buying guns at gun shows.

But gun control advocates worry that opposition from the powerful National Rifle Association and its allies in Congress will be too great to overcome. The new poll shows 51 percent said they believed laws limiting gun ownership infringe on the public’s constitutional right to possess and carry firearms.

The NRA released an online video Tuesday that called Obama an “elitist hypocrite” for having armed Secret Service agents protect his daughters at school while not committing to installing armed guards in all schools. The NRA insists that the best way to prevent more mass shootings is to give more “good guys” guns and put an armed security officer in every school in the country.

White House officials signaled that Obama would seek to rally public support for the measures he puts forward, perhaps holding events around the country or relying on Organizing for America, his still-operational presidential campaign.

Obama’s appeal to the public starts with his Wednesday announcement, where he will be joined by children who wrote to him after the Connecticut shooting asking for more gun controls.

White House officials, seeking to avoid setting the president up for failure, have emphasized that no single measure — even an assault weapons ban — would solve the scourge of gun violence. But without such a ban, or other sweeping Congress-approved measures, it’s unclear whether executive actions alone can make any noticeable difference.

“It is a simple fact that there are limits to what can be done within existing law,” White House spokesman Jay Carney said Tuesday. “Congress has to act on the kinds of measures we’ve already mentioned because the power to do that is reserved by Congress.”

According to a lobbyist briefed Tuesday, Obama will present a three-part plan focused on gun violence, education and mental health.

The president will call for a focus on universal background checks. Some 40 percent of gun sales take place without background checks, including those by private sellers at gun shows or over the Internet, according to the Brady Campaign to Prevent Gun Violence.

The president will call for banning assault weapons and limiting ammunition magazines to 10 rounds or fewer, and also propose a federal statute to stop “straw man” purchases of guns and crack down on trafficking rings. He’ll order federal agencies to conduct more research on gun use and crimes, something Republican congressional majorities have limited through language in budget bills, the lobbyist said.

The president’s framework is based on recommendations from Vice President Joe Biden, who led a wide-ranging task force on gun violence. Beyond the gun control measures, Biden also gave Obama suggestions for improving mental health care and addressing violent images in video games, movies and television.

The vice president’s proposals included 19 steps that could be achieved through executive action.

Obama may order the Justice Department to crack down on people who lie on background checks; only a tiny number are now prosecuted. Such a step has support from the NRA, which has consistently argued that existing laws must be enforced before new ones are considered.

Obama also could take steps ordering federal agencies to make more data on gun crimes available and conduct more research on the issue, something Republican congressional majorities have limited through language in budget bills. And he may order tougher penalties against gun trafficking and give schools flexibility to use grant money to improve safety.

States and cities have been moving against gun violence as well.

New York Gov. Andrew Cuomo on Tuesday signed into law the toughest gun control law in the U.S., and the first since the Connecticut school shootings. The law includes a tougher assault-weapons ban and provisions to try to keep guns out of the hands of mentally ill people who make threats.

The NRA criticized the bill in statement. “These gun control schemes have failed in the past and will have no impact on public safety and crime,” the group said.

In Washington, it’s unclear how much political capital Obama will exert in pressing for congressional action.

The White House and Congress will soon be consumed by three looming fiscal deadlines, each of which is expected to be contentious. And the president has also pledged to tackle comprehensive immigration reform early this year, another effort that will require Republicans’ support and one in which Obama may be more likely to get their backing.

Sen. Mitch McConnell, the chamber’s top Republican, has warned the White House that it will be at least three months before the Senate considers gun legislation. And Senate Majority Leader Harry Reid, a Democrat, has said immigration, not gun control, is at the top of his priority list after the fiscal fights.

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Associated Press writers Julie Pace, Erica Werner, Ken Ritter, Josh Lederman Michael Gormley and Michael Virtanen contributed to this report.

Copyright 2013 The Associated Press.