At the White House appearance, the president — surrounded by the mothers of the Connecticut shooting victims — called on Americans to pressure lawmakers into backing gun control initiatives currently making their way to the Senate floor.
Obama expressed astonishment that so soon after December's slaughter at an elementary school in Newton, Conn., there appeared to be fading political will to tackle gun control.
"That's not who we are," he said. "Less than 100 days ago that happened ... and the entire country pledged we would do something about it and this time would be different. Shame on us if we've forgotten .... I haven't forgotten those kids."
Obama urged lawmakers: "Don't get squishy."
"What we're proposing is not radical, it's not taking away anyone's gun rights, it's something that if we are serious, we will do.... Now's the time to turn that heartbreak into something real."
Obama had barely finished speaking when a Republican senator emerged to illustrate the very resistance that is confronting the president's efforts to push meaningful gun control measures through Congress.
Utah's Mike Lee reiterated his pledge to filibuster Obama's gun control proposals along with fellow Republicans Rand Paul and Ted Cruz.
"The proposals the president is calling for Congress to pass would primarily serve to reduce the constitutionally protected rights of law-abiding citizens while having little or no effect on violent crime," Lee said in a statement.
"It is deeply unfortunate that he continues to use the tragedy at Newtown as a backdrop for pushing legislation that would have done nothing to prevent that horrible crime."
Obama made his White House remarks as investigators in Connecticut released details of the stunning cache of weapons and ammunition they recovered at the home shared by Adam Lanza, the perpetrator of the Newtown shooting, and his mother, who was also gunned down by her son last December.
"These weapons were legally purchased under our current laws," Connecticut Gov. Dannel Malloy said following the release of the details of police search warrants.
"I don’t know what more we can need to know before we take decisive action to prevent gun violence. The time to act is now."
Also recovered from the Lanza home: a book entitled "The NRA Guide to the Basics of Pistol-Shooting" and two NRA certificates bearing Ryan and Nancy Lanza's names.
The National Rifle Association, a powerful lobby group that contributes significant funding to the campaigns of lawmakers, claimed Thursday that the police records are false.
"There is no record of a member relationship between Newtown killer Adam Lanza, nor between Nancy Lanza, A. Lanza or N. Lanza with the National Rifle Association," the organization said in a statement.
"Reporting to the contrary is reckless, false and defamatory."
The NRA has long insisted it merely advocates for the Second Amendment rights of average American citizens. In recent years, however, there's been increasing evidence that the lobby group receives funding from gun manufacturers and private security firms.
Gun control is a hot-button issue in the United States, the most heavily armed nation on Earth. There are estimated 300 million guns in circulation, with at least one firearm in as many as 45 per cent of the nation's homes.
Americans have a historic attachment to guns stemming from a long-held distrust of big government. Early settlers were pioneers and revolutionary rebels, and guns are therefore considered central to the American identity, particularly in the south and the West.
But gun control advocates insist the Second Amendment of the U.S. Constitution, guaranteeing the right to bear arms, has been twisted by gun enthusiasts to a degree never intended by the country's Founding Fathers, who couldn't have imagined the firepower of today's guns.
Nonetheless, an attempt to outlaw deadly assault weapons seems futile in 2013. Harry Reid, the Senate majority leader, has already cut a proposed assault weapons ban from the current gun control bill, fearing it would doom the legislation if it remained.
The assault weapons ban is still, however, expected to get a vote as an amendment to the main gun control bill.
That bill proposes universal background checks, tougher punishments for illegal gun trafficking and more money for school security.
Obama made the case for beefing up background check procedures on Thursday, pointing out that nine out of 10 Americans offer support for the measure.
"How often do 90 per cent of Americans agree on anything?" he said.
The NRA, however, opposes tougher background checks.
Gun control advocates across the country tried to regain momentum on the issue on Thursday as they held dozens of rallies and other events in a national "day of action." Their aim was to pressure state and federal lawmakers into voting in favour of gun control.
"If it saves one life, and one more mom from going what I went through, let's do this," Mari Bailey, whose son, Michael, was shot and killed 10 years ago by an acquaintance, said at an event in Phoenix.