Obama was to announce the measures Wednesday at a White House event that will bring together law enforcement officials, lawmakers and children who wrote the president about gun violence following last month's shooting of 20 young students and six adults at an elementary school in Newtown, Conn.
The president also invited families of the Newtown victims and survivors of the horrific shooting to the White House Wednesday.
The broad package Obama will unveil will also include efforts to stop bullying and boost availability of mental health services.
But Congress would have to approve the bans on assault weapons and ammunition magazines holding more than 10 bullets, along with a requirement for universal background checks on gun buyers. Some gun control advocates worry that opposition from Republicans and conservative Democrats, as well as the National Rifle Association, will be too great to overcome.
"We're not going to get an outright ban," Rep. Carolyn McCarthy, D-N.Y., said of limits on assault weapons. Still, McCarthy, a leading voice in Congress in favor of gun control, said she would keep pushing for a ban and hoped Obama would as well.
White House officials, seeking to avoid setting up the president for failure, have emphasized that no single measure — even an assault weapons ban — would solve a scourge of gun violence across the country. But without such a ban or other sweeping, congressionally-approved measures, it's unclear whether executive actions alone could 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."
Nearly six in 10 Americans want stricter gun laws in the aftermath of the shootings in Connecticut, with majorities favoring a nationwide ban on military-style, rapid-fire weapons and limits on gun violence depicted in video games, movies and TV shows, according to a new Associated Press-GfK poll.
New York Gov. Andrew Cuomo on Tuesday signed into law the toughest gun control law in the nation, 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.
According to a lobbyist briefed Tuesday, Obama will present a three-part plan focused on gun violence, education and mental health. He'll call for:
— A focus on universal background checks. Right now some 40 percent of gun sales take place without background checks, including by private sellers at gun shows or over the Internet, according to the Brady Campaign to Prevent Gun Violence.
— A ban on assault weapons and limiting ammunition magazines to 10 rounds or fewer.
— A federal statute to stop "straw man" purchases of guns and crack down on trafficking rings.
— More anti-bullying efforts; more training for teachers, counselors and principals; and funding for schools for more counselors and resource officers.
Obama also will order federal agencies to conduct more research on gun use and crimes, the lobbyist said, something Republican congressional majorities have limited through language in budget bills.
On mental health, Obama will focus on more availability of mental health services, training more school counselors and mental health professionals, and mental health first aid training for first responders, according to the lobbyist, who was not authorized to discuss the plan publicly before the president's announcement and requested anonymity.
The president's framework is based on recommendations from Vice President Joe Biden, who led a wide-ranging task force on gun violence. The vice president's proposals included 19 steps that could be achieved through executive action.
Obama also may order the Justice Department to crack down on people who lie on gun-sale 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.
And Obama may give schools flexibility to use grant money to improve safety. But he is not expected to call for armed guards in schools, a position promoted by the NRA.
The gun lobby 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.
Gun control proponent Rep. Bobby Scott, D-Va., who met with Biden on Monday, said the president is also likely to take executive action to ensure better state reporting of mental health and other records that go into the federal background check database. But he, too, acknowledged there were clear limits to what Obama can do without Congress' say-so.
"You can't change the law through executive order," Scott said.
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.
During his announcement Wednesday, Obama will be joined children from across the U.S. who wrote letters to him about gun violence and school safety.
One of those children, a Maryland 8-year-old named Grant, wrote: "It's a free country but I recommend there needs (to) be a limit with guns. Please don't let people own machine guns or other powerful guns like that."
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. 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.
Senate Republican leader Mitch McConnell of Kentucky 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, D-Nev., has said immigration, not gun control, is at the top of his priority list after the fiscal fights.
House Republican leaders are expected to wait for any action by the Senate before deciding how — or whether — to proceed with any gun measure.