Gun control long has been a politically difficult subject.
"The fact that this problem is complex can no longer be an excuse for doing nothing," Obama said. "The fact that we can't prevent every act of violence doesn't mean we can't steadily reduce the violence."
The president, who expended little political capital on gun control despite a series of mass shootings in his first term, bristled at suggestions that he had been silent on the issue during his first four years in office. But he acknowledged that Friday's deadly shooting in Connecticut had been "a wake-up call for all of us."
Along with asking Congress to reinstate the assault weapons ban, Obama asked lawmakers to pass legislation that would close the gun show "loophole," which allows people to purchase firearms from private dealers without a background check. Obama also said he wanted Congress to pursue the possibility of limiting high-capacity ammunition clips.
Gunmen have used high-capacity ammunition clips and magazines to kill large numbers of people quickly in this year's mass shootings. Inside Sandy Hook Elementary, police said, Lanza needed just 10 minutes to shoot and kill 20 children and six adults. Each was shot multiple times with a high-powered rifle.
The president's announcement Wednesday underscores the urgency the White House sees in formulating a response to the Newtown shooting. The massacre has prompted several congressional gun rights supporters to consider new legislation to control firearms, and there is some concern that their willingness to engage could fade as the shock and sorrow over the Newtown shooting eases.
Appealing to gun owners, Obama said he believes in the Second Amendment and the country's strong tradition of gun ownership. And he said "the vast majority of gun owners" in America are responsible.
"I am also betting that the majority, the vast majority, of responsible, law-abiding gun owners would be some of the first to say that we should be able to keep an irresponsible, law-breaking few from buying a weapon of war," Obama said.
The president challenged the National Rifle Association, the country's most powerful gun lobby and key backer of many Republican politicians, to join the broader effort to reduce gun violence as well.
"Hopefully they'll do some self-reflection," Obama said of the NRA.
The NRA made its first comments since the Newtown shooting on Tuesday, promising to offer "meaningful contributions to help make sure this never happens again."
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