Many members of Congress from both parties are also skeptical that some of the proposed new restrictions on gun sales can be effective, much less pass.
"Nothing the president is proposing would have stopped the massacre at Sandy Hook," Republican Sen. Marco Rubio of Florida said. "President Obama is targeting the 2nd Amendment rights of law-abiding citizens instead of seriously addressing the real underlying causes of such violence."
Senate Majority Leader Harry Reid, a Democrat and gun owner, told a Las Vegas TV station Friday, "Is [the assault weapons ban] something that can pass the Senate? Maybe. Is it something that can pass the House? I doubt it. So I think there are things that we know we can do."
Before the announcement, the White House downplayed challenges facing individual aspects of gun-control proposals -- most notably the assault weapons ban -- stressing that no single measure can solve the epidemic of gun violence sweeping the country. They also pointed to successful steps on guns already taken on the state level.
New York State, for instance, approved the nation's most stringent gun-control law Tuesday, tightening a ban on assault-style weapons and beefing up protections to keep guns from the mentally ill.
Obama might travel the country seeking to leverage popular support for his proposals to urge action in Congress, officials said. He is also expected to mobilize his network of campaign supporters to participate in advocacy on guns.
"This will not happen unless the American people demand it," Obama said today of his plan. "If parents and teachers, police officers and pastors, if hunters and sportsmen, if responsible gun owners, if Americans of every background stand up and say, enough, we suffered too much pain and care too much about our children to allow this to continue, then change will come. That's what it's going to take."
Dozens of kids have written to the president about gun violence, officials said, including 8-year-old Grant Fritz of Maryland, who wrote in a letter released by the White House, "there should be some changes in the law with guns. It's a free country, but I recommend there needs be [sic] a limit with guns."
"Their voices should compel us to change," Obama said of the children.
Obama was joined for his announcement by seven cabinet secretaries, including Attorney General Eric Holder, Education Secretary Arne Duncan and Homeland Security Secretary Janet Napolitano, other local law enforcement leaders and mayors, and the families of victims and survivors of the Newtown shooting.
Many of Obama's proposals have strong support in the latest ABC News-Washington Post poll released Monday.
Eighty-eight percent of Americans favor expanding required background checks to buyers at gun shows; 76 percent favor checks on anyone buying ammunition.
New restrictions on high-capacity magazines are backed by 65 percent of Americans in the poll, with 58 percent supporting a ban on the sale of assault-style weapons. Thirty-nine percent oppose such a ban.
The NRA's proposal to place an armed guard in every school received 55 percent support in the survey.