Updated 2:56 p.m. -- President Barack Obama unveiled sweeping new policies Wednesday aimed at limiting gun violence, teeing up a political showdown that will pit the broad public popularity for many gun control measures against Congress’s tepid appetite for approving the most stringent restrictions on gun ownership.  

"While there is no law or set of laws that can prevent every senseless act of violence completely, no piece of legislation that will prevent every tragedy, every act of evil," Obama said at a mid-day announcement at the White House, "if there's even one thing we can do to reduce this violence, if there's even one life that can be saved, then we've got an obligation to try it."

Acknowledging the difficulty of the Congressional fight ahead, Obama appealed for public support, slamming - as he did in a press conference earlier this week - conservative commentators and the most vocal pro-gun activists for "ginning up" opposition to gun reforms for political reasons. 

"I will put everything I've got into this and so will Joe [Biden], but I tell you, the only way we can change is if the American people demand it," he said. 

Some of the main legislative proposals backed by Obama and Vice President Joe Biden are:

• requiring criminal background checks on all gun sales, including private sales    
• banning "military-style" assault weapons    
• limiting ammunition magazines to 10 rounds      
• strengthening penalties for gun trafficking 

"The most important changes we can make depend on Congressional action," Obama said. "They need to bring these proposals up for a vote and the American people need to make sure that they do."

Related Information: Gun Violence Fact Sheet | Gun Violence Executive Summary | Gun Violence Reduction Executive Actions 

The president also signed a series of 23 executive actions - free from a Congressional blockade -- intended to strengthen existing laws, augment mental health measures and promote federal research on gun crime through the Centers for Disease Control. 

The executive actions announced included stricter prosecution of would-be gun buyers who fail background checks as well as new requirements for federal law enforcement to trace guns recovered in criminal investigations. 
 

The president's recommendations also direct administration officials to "clarify that the Affordable Care Act does not prohibit doctors asking their patients about guns in their homes" and to "release a letter to health care providers clarifying that no federal law prohibits them from reporting threats of violence to law enforcement authorities." 

Obama and Biden were joined at the White House event by families of the Newtown school shooting victims as well as by four children who wrote the president after the tragedy that left 20 young students dead. 

"This is our first task as a society: keeping our children safe," Obama said at the beginning of his remarks. "This is how we will be judged, and their voices should compel us to change."

Biden, who led the presidential task-force on gun safety in the wake of the Newtown shootings, praised the activists who met with his staff over the last week to help build the list of recommendations. 

"The world has changed and it's demanding action," Biden said. 

While some of Obama's long-expected proposals - like universal background checks - garner overwhelming public support, the outlawing of certain types of weapons may be less of a slam dunk for lawmakers eager to appease constituents. 

A recent poll from the Pew Research Center showed that a majority of Americans -- 55 percent -- back a ban on "assault-style weapons," with 40 percent saying they don't approve of a ban. But a partisan breakdown shows that only about four in ten Republicans support such restrictions, compared to a broad majority of Democrats. 

Democrats in Congress have already voiced doubts about the feasibility of the president's most ambitious proposals. 

"We're not going to get an outright ban" on assault weapons, Democrat Rep. Carolyn McCarthy of New York bluntly said yesterday.

 "[Senate Majority Leader] Reid has said he doesn't know whether he has the votes (for an assault weapons ban)," she added. "There's heavy lifting, so are we going to waste time on heavy lifting? Or are we going to try to work on doing something that could actually get passed?"

Related: Obama's gun plans spark little enthusiasm with key lawmakers

Supporters are more optimistic about background checks and magazine restrictions. 

Senate Judiciary Committee Chairman Patrick Leahy announced Wednesday that his panel will hold its first hearing on issues relating to gun violence on Jan. 30.

In his remarks Wednesday, Obama anticipated opponents' reactions to his proposals. 

"This will be difficult," he said. "There will be pundits and politicians and special interest lobbyists publicly warning of a tyrannical all-out assault on liberty. Not because that's true, but because they want to gin up fear or higher ratings or revenue for themselves, and behind the scenes they will do everything they can to block any commonsense reform and make sure nothing changes whatsoever."

The National Rifle Association, the country's most powerful gun lobby, released a statement Wednesday afternoon in response to the president's remarks.

"We look forward to working with Congress on a bi-partisan basis to find real solutions to protecting America's most valuable asset - our children. Attacking firearms and ignoring children is not a solution to the crisis we face as a nation," the NRA wrote. "Only honest, law-abiding gun owners will be affected and our children will remain vulnerable to the inevitability of more tragedy."

That statement was relatively muted in comparison to the group's controversial ad released Tuesday night, which criticized Obama's dismissal of the gun lobby's proposal to increase armed security in schools. 

"Are the president's kids more important than yours?" a narrator asks in the short ad. "Then why is he skeptical about putting armed security in our schools when his kids are protected by armed guards at their schools? Mr. Obama demands the wealthy pay their fair share of taxes, but he's just another elitist hypocrite when it comes to a fair share of security."

Related: White House calls NRA 'repugnant,' 'cowardly' for invoking president's children in ad

The ad prompted outcry from observers who said the First Family should be off limits for such advertisements, while NRA backers say their focus is on school safety rather than on the president's daughters themselves. 

"Whoever thinks the ad is about President Obama's daughters are missing the point completely or they're trying to change the subject," said spokesman Andrew Arulanandam. "This ad is about keeping our children safe. And the president said he was skeptical about the NRA proposal to put policemen in all schools in this country. Yet he and his family are beneficiaries of multiple law enforcement officers surrounding them 24 hours a day." 

White House spokesman Jay Carney shot back that the ad is "cowardly." 

"Most Americans agree that a president's children should not be used as pawns in a political fight," he said. "But to go so far as to make the safety of the President's children the subject of an attack ad  is repugnant and cowardly."

NBC's Mark Murray, Frank Thorp, Ali Weinberg and Kelly O'Donnell contributed to this report.