The president said he would present a comprehensive road map for curbing gun violence within days. His plan will be based on recommendations from Vice President Biden's gun task force and is expected to include both legislative proposals and steps Obama can implement by himself using his presidential powers.
But the most sweeping and contentious elements - including an assault-weapons ban - will require approval from a Congress that has been loath to tackle gun-control legislation for more than a decade. The politically powerful NRA has vowed to fight any measure that would limit access to guns and ammunition, a hard-line position that could sway some Republicans and conservative Democrats.
Despite the opposition, Obama said he would "vigorously pursue" measures to tighten gun laws. "My starting point is not to worry about the politics," he said.
The president's new resolve follows a lack of movement in tackling gun violence throughout much of his first term, despite several high-profile shootings. He called the Dec. 14 massacre of 20 children and six adults at Sandy Hook Elementary School the worst day of his presidency and vowed to take action.
Parents of the slain Connecticut children added their voices to the national dialogue Monday. Members of the newly formed group Sandy Hook Promise called for an open-minded discussion about a range of issues, including guns, mental health and safety in schools and other public places.
And lawmakers in New York state pressed ahead with what would be the nation's first gun-control measure approved since the school shootings. Among the items in a tentative agreement in the state legislature are further restrictions on the state's ban on assault weapons, limits on the size of magazines to seven bullets, down from the current 10, and more stringent background checks for sales.
White House officials believe that moving swiftly on gun proposals at a national level, before the shock over the Newtown shooting fades, gives Obama the best chance to get his proposals through Congress. Several gun-rights lawmakers, including Democratic Sen. Joe Manchin of West Virginia and Republican Rep. Jack Kingston of Georgia, said in the days following the shooting that they were open to discussing possible control measures.
Seeking to keep up the pressure on lawmakers, Obama said Monday that if "everybody across party lines was as deeply moved and saddened as I was by what happened in Newtown, then we're going to have to vote based on what we think is best."
Officials said Obama and Biden met Monday afternoon to discuss the vice president's recommendations. Ahead of that meeting, Biden huddled with a dozen House Democrats who have formed their own gun-violence task force and whose political muscle will be needed to push legislation through Congress.
The president, without mentioning the NRA, said that some gun-rights groups have "a pretty effective way of ginning up fear on the part of gun owners that somehow the federal government's about to take all your guns away."
Seeking to ease those fears, Obama insisted that responsible gun owners who have weapons for protection or hunting "don't have anything to worry about" under the proposals he will push.
The assault-weapons ban, which Obama has long supported, is expected to face the toughest road on Capitol Hill. Congress passed a 10-year ban on the high-grade military-style weapons in 1994, but supporters didn't have the votes to renew it once it expired in 2004.
Senate Majority Leader Harry Reid (D., Nev.) on Friday predicted that a ban might win Senate approval but he doubted it could pass in the Republican-led House.
Obama will also need congressional help to limit high-capacity ammunition magazines, like the ones used by the Newtown shooter, and to require background checks for anyone seeking to purchase a gun. Some gun-control advocates, including the Brady Campaign to Prevent Gun Violence, are urging Obama to make the broader background checks his top priority, believing it has the best chance of winning congressional approval.
The Brady Campaign said that about 40 percent of gun sales happen with no background checks, such as at gun shows and by private sellers over the Internet or through classified ads.
Among the executive actions Biden is believed to have recommended to Obama are tougher penalties for people who lie on background checks, elevating gun trafficking to a felony charge, and ending limits that make it harder for the government to research gun violence.