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President Obama will unveil a comprehensive effort to address gun violence as he calls on Congress to ban military-style assault weapons and high-capacity magazines as part of an aggressive agenda that is drawing resistance from some Republican lawmakers and gun rights advocates.

The president, facing criticism over his potential use of executive action to push multiple gun control measures, will be joined by children who wrote him letters about gun violence and school safety at a press conference shortly before noon on Wednesday.

"(Obama) believes and knows that most all gun owners are highly responsible, they buy their guns legally, and they use them safely," White House Press Secretary Jay Carney said Tuesday. "He also has seen and believes that most gun owners support the idea of commonsense measures to prevent people who shouldn't have guns from getting them."

Carney, without getting into specifics, vowed a "comprehensive approach." Two Democratic aides later confirmed that the legislative plank would include a push for universal background checks, a ban on high-capacity magazines and renewal of the assault weapons ban.

The announcement -- the product of a task force led by Vice President Biden -- is cloaked in controversy. That the announcement would include children as a backdrop added another level.

Roger Pilon, with the libertarian-leaning Cato Institute, criticized the staging as "tacky," saying Obama has "carved up the population on a very emotional issue."

Yet in the wake of a school massacre last month in Connecticut that left 20 first-graders dead, as well as six educators, the president has stressed that children's lives could be on the line. Obama, like prior presidents, often invites members of the public to act as a backdrop for certain policy announcements. They are always carefully selected -- over the summer, he invited college students for a speech about student loan rates and middle-class taxpayers to another talk on extending tax rates. The White House has also invited doctors for speeches on the health care overhaul.

The substance of Obama's announcement Wednesday, though, is likely to cause the biggest stir.

Sources say he's weighing as many as 19 possible actions he could take through executive order. Those options could include more aggressively enforcing existing gun laws, beefing up national research on guns and ordering stricter action against people who lie on gun sale background checks. They could include ordering tougher penalties for gun-trafficking offenses and ordering federal agencies to make data on gun crimes more readily available.

Carney on Tuesday declined to specify what actions the president might take via executive order.

The president, though, has already voiced support for separate legislative measures in Congress, like the renewal of the assault weapons ban. That is expected to face the toughest opposition in Congress. But Biden, who led the gun violence task force and met with the president Monday, indicated the group is also pressing for limits on high-capacity magazines -- as well as background checks for anyone seeking to purchase a gun. Carney reiterated Tuesday that Obama still wants those measures pursued.

Such changes "make sense," Obama said. He said lawmakers will have to "examine their own conscience" in the debate ahead.

The president's push is drawing resistance from Republicans in Congress. Rep. Steve Stockman, R-Texas, is now vowing to try to impeach Obama if he takes any action via executive order.

He called the plan to implement some controls administratively "an unconstitutional and unconscionable attack on the very founding principles of this republic."

"I will seek to thwart this action by any means necessary, including, but not limited to, eliminating funding for implementation, defunding the White House, and even filing articles of impeachment," Stockman said.

The White House also has been at odds with the National Rifle Association, as it tries to keep focus on gun control measures in the wake of the Connecticut school massacre. The NRA, by contrast, has called for an increase in school security and a closer look at the entertainment and video game industries.

During his press conference Monday, Obama accused critics of his approach of "ginning up fear on the part of gun owners."

In response, NRA spokesman Andrew Arulanandam said: "The president should go talk to the people buying firearms and ask them why they're buying firearms."

States and cities have been moving against gun violence as well. In New York, Gov. Andrew Cuomo on Tuesday signed into the law the most restrictive gun policy in the nation, after he delivered a fiery speech last week on the need to make changes.

"This is a scourge on society," Cuomo said Monday night, exactly one month after the massacre. "At what point do you say, `No more innocent loss of life'?"

The bill had bipartisan support, with the leader of the Republican-held state Senate saying it does not infringe on the Constitution's Second Amendment, which guarantees the right of citizens to bear arms.

The New York measure calls for a tougher assault weapons ban and restrictions on ammunition and the sale of guns. It also would create a more powerful tool to require the reporting of mentally ill people who say they intend to use a gun illegally and would address the unsafe storage of guns.

At the national level, advocacy groups have been pushing Obama to order the Justice Department to crack down on those who lie on background checks; only a tiny number are now prosecuted. Such a step has support from the NRA, which has consistently argued that existing laws must be enforced before new ones are considered.

The Brady Campaign to Prevent Gun Violence says some 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.

The Associated Press contributed to this report.