President Barack Obama backed a new bid to revive an assault weapons ban and other new gun laws, as traumatized US politicians wrestled with the aftermath of a sickening school massacre.
Obama also called an ardently pro-gun senator who has shifted his position on firearms laws since Friday's carnage in Connecticut and has begun meeting top cabinet officials to consider his options, his spokesman Jay Carney said.
The killings of 26 people, including 20 children, at a Newtown elementary school sent the country into shock, and may have shifted the political debate on firearms in US society, after years of gun lobby ascendancy.
Carney said that Obama is "actively supportive" of an effort by Democratic Senator Dianne Feinstein to write a bill early next year to reintroduce a ban on deadly assault weapons that expired in 2004.
Obama aides said after previous mass shootings that the president supported reintroducing a ban on weapons like the one used by Adam Lanza to gun down six and seven-year-olds, but he never put political muscle behind such a push.
Carney said Obama would also be interested in any move to ban high-capacity clips -- magazines that hold dozens of rounds -- and to close the so-called "gun show loophole" that allows unlicensed individuals to sell guns privately.
"He is heartened... by what we have all heard from some members of Congress who have been long-time opponents of gun control measures, common-sense gun control measures like the assault weapons ban and the like," Carney said.
Feinstein has said her bill would ban by name at least 100 military-style semi-automatic assault weapons, and would curb the transfer, importation and the possession of such arms.
"It's going to be strong, and it's going to be definitive," she said.
But once outrage from the Newtown massacre fades, prospects for Feinstein's bill remain uncertain and every piece of legislation is subject to intense amendment and pressure from various lobby groups.
But the California senator said that the tragedy was so acute in Newtown, a "sea change" in gun politics was possible.
"This is so graphic in people's minds, the smallness and beauty of these children, is so graphic, the loss is so dramatic," she said.
The most well known gun lobby group, the National Rifle Association, spoke up about the school carnage for the first time Tuesday, saying it was "shocked" and pledged to hold a news conference on Friday.
The White House said that Obama's vow on Sunday that gun tragedies "must end" could only be realized in part by new gun controls.
To that end, he met Education Secretary Arne Duncan, Health Secretary Kathleen Sebelius and Attorney General Eric Holder on Monday to discuss a "comprehensive" effort, possibly including new efforts to stop the mentally ill from getting weapons.
Obama also Tuesday called West Virginia Senator Joe Manchin, a pro-gun politician who may now back an assault weapons ban who may be a useful ally in the days ahead.
The right to bear arms is enshrined in the Second Amendment to the US Constitution, and many political leaders are pro-gun for political and philosophical reasons but the political winds may be shifting.
"We need to accept the reality that we're not doing enough to protect our citizens," Senate Democratic Majority leader Harry Reid said Tuesday.
"We must engage in a thoughtful debate about how to change laws and a culture that allows violence not to continue to grow. Every idea should be on the table."
Several leading Republican senators, while shocked by the school massacre and accepting something had to be done, were not ready to commit this early to specific anti-gun legislation or to rule out gun ownership altogether.
"The bigger point here is what public policy can we advocate that would keep all dangerous weapons out of the hands of criminals and those who are mentally unstable," said Senator Marco Rubio.
"I've always supported... reasonable public policy changes that accomplish that, but also with the recognition that the Second Amendment right to bear arms is not a policy decision, it is a constitutional principle."
Republican Senator Jeff Sessions told AFP that new gun legislation would "definitely be on the table" next year.
Senator John McCain, asked about tighter controls on assault weapons, said: "I think we need to have a conversation about all aspects of this tragedy to see that it doesn't happen again.'
But Republican Senator Lindsey Graham argued that reinstituting an assault weapons ban might "give a false sense of security."
"I don't know what the government can do when you have somebody this disturbed. Take everybody's guns away? Start putting people in preventive detention who, you know, act odd?" he said.
"How do you prevent mass murder? Do you take every sharp object in the nation off the table? That's not practical."
"I just don't want to make people think that a bunch of politicians can solve the problem when they haven't."
America has suffered an epidemic of gun violence over the last three decades, including 62 mass shooting sprees since 1982, three of the deadliest in the second half of this year alone.