Rolling out a wide-ranging plan for executive and legislative action to curb gun violence, Mr Obama set up a fierce clash with the powerful U.S. gun lobby and its supporters in Congress, who will resist what they see as an encroachment on constitutionally protected gun rights.
Mr Obama presented his agenda at a White House event in front of an audience that included relatives of some of the 20 first-graders who were killed along with six adults by a gunman on December 14 at Sandy Hook Elementary School in Newtown, Connecticut.
"We can't put this off any longer," Obama said, vowing to use "whatever weight this office holds" to make his proposals reality. "Congress must act soon."
Until now, Mr Obama had done little to rein in America's gun culture during his first four years in office. But just days before his second inauguration, he appears determined to champion gun control in his next term with a concerted drive for tighter laws and other steps aimed at preventing new tragedies like the one at Newtown.
The proposals stem from a month-long review led by Vice President Joe Biden, who on orders from Obama met with advocates on both sides, including representatives from the weapons and entertainment industries.
Mr Obama's plan calls on Congress to renew a prohibition on assault weapons sales that expired in 2004, a requirement for criminal background checks on all gun purchases, including closing a loophole for gun show sales, and a new federal gun trafficking law - long sought by big-city mayors to keep out-of-state guns off their streets.
He also announced 23 steps he intends to take immediately without congressional approval. These include improvements in the existing system for background checks, lifting the ban on federal research into gun violence, putting more counselors and "resource officers" in schools and better access to mental health services.
Assault weapons battle
The most politically contentious piece of the package is Mr Obama's call for a renewed ban on military-style assault weapons, a move that Republicans who control the House of Representatives are expected to oppose.
The Newtown gunman, 20-year-old Adam Lanza, used a Bushmaster AR-15 type assault rifle to shoot his victims, many of them 6- and 7-year-olds, before killing himself.
Underscoring the tough political fight ahead, the National Rifle Association, launched a scathing advertising campaign against Obama's gun control effort and deployed its representatives in force on Capitol Hill.
The NRA, which says it has about 4 million members, took aim at Obama in a stinging TV and Internet spot, accusing him of being "just another elitist hypocrite" for accepting Secret Service protection for his two daughters but turning down the lobby group's proposal to put armed guards in all schools.
As he announced the new gun measures, Mr Obama was flanked on the stage by children from around the country chosen from among those who sent letters to him about gun violence and school safety.
"We should learn from what happened at Sandy Hook. I feel really bad," a boy wrote in a portion that Mr Obama read from the podium.
With gun ownership rights enshrined in the US Constitution, gun restrictions have long been a divisive - and risky - issue in American politics.
But polls show that public sentiment shifted in favour of increased gun-control measures after the Newtown shooting, and Mr Obama hopes to take advantage while there is a mood for action in Washington.
However, the White House is mindful that the clock is ticking. The usual pattern after US shooting tragedies is that memories of the events soon fade, making it hard to sustain a push for gun policy changes.
Mr Obama acknowledged the political challenges but made clear that he is prepared to take on the NRA, despite its widespread support among Republicans and significant backing among Democrats.
He warned that opponents of his effort would try to "gin up fear" and urged lawmakers to think more about the safety of schoolchildren than trying to "get an 'A' grade from the gun lobby that supports their campaign."
Mr Obama's plan appears to tread cautiously on the question of whether violent movies and video games contribute to the gun violence, which would open up issues of freedom of expression.
A senior administration official said, however, that Mr Obama would be asking for $10 million for the US Centers for Disease Control and Prevention to study the root causes of gun violence, including any relationship to video games and media images.
Seeking to jump-start his plan, Mr Obama also nominated Todd Jones to head the Bureau of Alcohol, Tobacco and Firearms, quietly abandoning Andrew Traver, whose nomination for the job has long been stalled. Jones is currently the acting director of the law enforcement agency.