WASHINGTON (CNN) -- A package of gun control proposals including a ban on assault weapons will be unveiled on Wednesday by President Barack Obama in response to last month's Connecticut school massacre.
Obama and Vice President Joe Biden will announce the proposals, White House spokesman Jay Carney told reporters on Tuesday.
They will be joined by a group of children who wrote letters to the president in the aftermath of the December 14 shooting rampage by a lone gunman who killed 20 students and six adults at a Newtown elementary school, Carney said.
Obama will propose legislative steps he previously has backed, such as a ban on assault weapons, restrictions on high-capacity ammunition magazines and strengthening federal background checks of people attempting to buy guns, according to Carney.
The president also will push for other steps that could include executive actions on his part that don't require congressional approval, Carney noted.
Biden led a panel assembled by Obama to examine gun control steps after the Newtown shootings, which sparked a fierce public debate over how to prevent such mass killings with guns.
Opponents led by the powerful National Rifle Association promise a political fight against gun control measures that they say will violate the constitutional right to bear arms.
An NRA spokesman said Tuesday the group has experienced what he called an "unprecedented" spike in membership numbers since new calls for gun control began in the past month.
Approximately 250,000 people have joined the organization's existing 4.25 million members, according to NRA spokesman Andrew Arulanandam.
"This is in direct response to the threats and accusations coming from"Obama and other political leaders, Arulanandam said, adding that "if anyone is wondering if the American people cared about the Second Amendment ... those numbers give a very clear answer."
In addition to new members, the NRA is also receiving an influx of financial contributions, he said.
"This is going to be a very expensive and hard-fought fight," Arulanandam noted.
The federal government estimates that more than 300 million non-military guns are owned or available for purchase in the United States.
At the White House, Carney acknowledged the challenge, saying: "If these things were easy, they would have been achieved already."
"It's something we have to do together," he said. "It's something that cannot be done by a president alone. It can't be done by a single community alone or a mayor or a governor or by Congress alone. We all have to work together."
Carney also reiterated Obama's belief in the Second Amendment right of citizens to be armed.
"He has made clear that he believes we ought to take common sense, and enact common sense measures that protect Second Amendment rights but prevent people who should not have weapons from obtaining them," he said.
Carney said the proposals Obama will present Wednesday would be his final version of the package recommended by Biden's team.
The recommendations by Biden's panel included as many as 19 executive actions, such as tougher enforcement of existing laws, legislators briefed by the vice president said Tuesday.
Obama could demand that agencies provide data for background checks that are supposed to accompany gun sales, ensuring that information included in the checks is as "comprehensive and complete as possible," Democratic Rep. Mike Thompson of California told CNN.
The president also could immediately appoint a director of the Bureau of Alcohol, Tobacco, Firearms and Explosives, which has been without a permanent chief for six years, Thompson said.
A Democratic member of Congress who was briefed on the recommendations said some of the 19 executive actions discussed included improving the way the government administers current law.
The legislator, speaking on condition of not being identified, cited loopholes in the federal database for background checks on gun sales as well as issues involving mental health checks as possibilities for executive action.
None of the legislators mentioned the NRA's call for armed guards at school as an option under consideration.
Obama has not ruled out issuing executive orders on some gun control measures to enforce laws already on the books, such as bolstering the way gun sales are tracked.
The president reiterated his desire on Monday for more robust background checks for gun buyers, keeping high capacity magazines away from criminals, and a ban on assault weapons.
"Will all of them get through this Congress? I don't know," Obama said. "But what's uppermost in my mind is making sure that I'm honest with the American people and members of Congress about what I think will work, what I think is something that will make a difference."
Working with Congress will be paramount in curbing gun violence, Thompson said, singling out a ban on high capacity magazines as an example of a measure that could garner Republican support. A full-scale assault weapon ban would be tougher to pass the GOP-controlled House, he argued.
Obama also said on Monday that the gun lobby was "ginning up" fears the federal government will use the Connecticut tragedy to seize Americans' guns. At least part of the frenzy is little more than marketing, he implied.
"It's certainly good for business," the president said, responding to a question about a spike in weapons sales and applications for background checks since the December killings.
Biden has said he's found widespread support for universal background checks and restrictions on the sale of high capacity magazines, which gun control advocates believe contribute to more bloodshed at mass shootings.
The influential NRA, among other gun rights groups, has vowed to fight any new gun restrictions -- like an assault weapon ban.
Gun control advocates, gun violence victims, the NRA, video game makers and others have met with the Biden-led task force.
In New York, New York Mayor Michael Bloomberg said Monday that more than 1 million people have signed a petition backed by his group, Mayors Against Illegal Guns, to tighten gun control laws in the wake of the Newtown shooting rampage.'
"For many Americans, this is the straw that broke the camel's back," he said.
A new Gallup poll released Monday showed 38% of Americans were dissatisfied with current gun laws and support stricter proposals. That was a 13 percentage point jump from a year ago.
The shift included a 17 percentage point increase in support for stricter gun control laws among men, compared to 10 percentage points for women, who traditionally have been more supportive of gun control legislation.
In New York -- where a week ago, Democratic Gov. Andrew Cuomo spelled out tough new gun control proposals -- the state Senate passed a series of new gun regulations in a 43-18 vote Monday night. The bill now goes to the state Assembly.
The tentative New York plan would include a statewide assault weapons registry and add a uniform licensing standard across the state -- altering the current system, in which each county or municipality sets a standard -- a state Senate source said.
Magazines could have no more than seven bullets under the would-be agreement, according to the source, among other provisions.
Discussions had percolated about crafting a law, similar to one in California, that allows mental health professionals to inform law enforcement if they believe their patient could pose a threat to themselves or others, the source said
Law enforcement authorities may then revoke the patient's license to carry a firearm and prevent them from having a gun for at least six months.
Across the country, more than a million people failed background checks to buy guns during the past 14 years because of criminal records, drug use or mental health issues, according to FBI figures. That figure, however, is a small fraction of overall gun sales.
CNN's Carol Cratty, Jim Acosta, and Kevin Liptak contributed to this report.