Prominent gun-rights advocates in the US Congress are calling for a national discussion about restrictions to stop gun violence, signalling that the horrific shooting at a Connecticut primary school could be a tipping point in a debate that has been dormant for years.
White House officials said President Barack Obama would make preventing gun violence a second-term policy priority.
But it was unclear what Obama would pursue or how, and aides said stricter gun laws would be only part of any effort.
The president has met with Vice President Joe Biden and a handful of Cabinet members to begin discussions on ways the country should respond to the Newtown shootings.
Among those in attendance were Attorney General Eric Holder, Education Secretary Arne Duncan, and Health and Human Services Secretary Kathleen Sebelius.
It remains to be seen whether Obama and Congress can turn their rhetoric into action or whether the shock over the Connecticut shootings will fade before they do.
Public opinion has shifted against tougher gun control in recent years, and the gun lobby is a powerful political force, particularly in Republican primaries.
Also, Obama has called for a national dialogue after other mass shootings during his presidency, only to see those efforts take a backseat to other pressing issues.
This time, the president has vowed to use "whatever power this office holds" to safeguard American children against gun violence, suggesting he may put political muscle behind an assault weapons ban.
He has long supported reinstating the ban, which expired in 2004, but never pressed for in his first term. Liberal Democrats on Capitol Hill are already laying the groundwork for legislation to outlaw the military-style arms.
Twenty children and six adults were killed when a gunman carrying a high-powered military-style rifle and other guns stormed Sandy Hook Elementary in Newtown, Connecticut, on Saturday.
"Everything should be on the table," West Virginia Senator Joe Manchin declared.
He is a conservative Democrat, avid hunter and lifelong member of the National Rifle Association.
Republican Senator Chuck Grassley of Iowa proposed a debate not just about guns but also about mental issues.
Virginia's Mark Warner, one of the few Senate Democrats who has found favour with gun rights groups, reversed course to back restrictions on assault weapons.
"The status quo is not acceptable anymore," he said.
Democratic Senate Majority Leader Harry Reid vowed Congress would soon "engage in a meaningful conversation and thoughtful debate about how to change laws and culture that allow violence to grow." The Senate Judiciary Committee will hold hearings on gun violence early next year.
The American public has been split over tougher gun laws, and there is no early indication that the Newtown shootings are changing many minds.
A Washington Post/ABC News poll conducted over the weekend showed 54 percent favour tougher laws, about the same as the 51 percent in favour earlier in the year.
Seven in 10 are opposed to banning the sale of handguns to anyone except law enforcement officers, the highest percentage since 1999.
Obama's spokesman reiterated his support for reinstating the assault weapons ban. Obama was outspoken in his calls for Washington to renew the ban during his 2008 White House run, but he made no effort to get it done during his first four years in office.
If Obama follows through on his pledge to make the stemming of gun violence a priority, he's likely to press for a broad approach.
He's previously called for improving mental health services for young people and instituting more effective policing strategies, though his rhetoric has never turned into a policy push.
Obama has said he believes the Constitution's Second Amendment guarantees an individual the right to bear arms and has spoken of a national heritage that cherishes hunting, shooting and the tradition of gun ownership. The president has signed laws letting people carry concealed weapons in national parks and in checked bags on Amtrak trains.
At the White House, press secretary Jay Carney said stricter gun control laws were part of the solution but not the only one.
He said the president would engage in "the coming weeks" in a process that includes input from law enforcement, mental health experts and lawmakers.
"It's a complex problem that will require a complex solution," Carney said. "No single piece of legislation, no single action will fully address the problem."
Democratic Senator Dianne Feinstein said she will introduce legislation next year to ban the sale of new assault weapons, as well as big clips, drums and strips of more than 10 bullets.
Police say the Newtown gunman, Adam Lanza, was carrying an arsenal of ammunition and used a high-powered rifle similar to the military's M-16.
White House officials said the president feels some urgency to address gun violence in the wake of the rampage.
But Obama is not expected to take any formal action before the end of the year given the all-consuming efforts to resolve the "fiscal cliff" and nominate new Cabinet secretaries.
Some gun control advocates urged Obama and lawmakers to act quickly, while the sorrow and shock of the Newtown shooting is still raw.
"It demands immediate national action," New York City Mayor Michael Bloomberg said. "It needs to be at the top of their agenda."
Since the shootings, the powerful National Rifle Association lobby has been silent.
Requests for comments have gone unanswered, and officials are turning down interview requests until they have more details.
Their 1.7 million-strong Facebook group has disappeared, and the group's Twitter account - which is a favourite platform to communicate with supporters - has not sent a message since before the grim reality of Connecticut's shootings set in.