Tears streaking his cheeks, President Barack Obama launched a final-year push Tuesday to tighten sales of firearms in the U.S., using his presidential powers in the absence of tougher gun restrictions that Congress has refused to pass.

The president struck a combative tone as he came out with plans for expanded background checks and other modest measures that have drawn consternation from gun rights groups, which Obama accused of making Congress their hostage. Palpable, too, was Obama's extreme frustration at having made such little progress on gun control since the killing of 20 first-graders in Connecticut confronted the nation more than three years ago.

"First-graders," Obama said woefully, resting his chin on his hand and wiping away tears as he recalled the 2012 massacre at Sandy Hook Elementary School. "Every time I think about those kids, it gets me mad."

Obama's 10-point plan to keep guns from those who shouldn't have them marked a concession by the president: He'll leave office without securing the new gun control laws he's repeatedly and desperately implored Congress to pass.

The National Rifle Association, the largest gun group, panned Obama's plan and said it was "ripe for abuse," although the group didn't specify what steps, if any, it will take to oppose or try to block it. Even Sen. Joe Manchin, a Democrat and gun-owner who co-wrote the bipartisan bill Obama supported in 2013, took issue with the president's move.

"Instead of taking unilateral executive action, the president should work with Congress and the American people, just as I've always done, to pass the proposals he announced today," Manchin said.

The centerpiece of Obama's plan is an attempt to narrow the loophole that exempts gun sales from background checks if the seller isn't a federal registered dealer. With new federal "guidance," the administration is clarifying that even those who sell just a few weapons at gun shows, flea markets or online can be deemed dealers and required to conduct checks on prospective buyers.

Whether that step can make a significant dent in unregulated gun sales is an open question, and one not easily answered.

Millions of guns are sold annually in informal settings outside of gun shops, including many through private sales arranged online. But the Obama administration acknowledged it couldn't quantify how many gun sales would be newly subjected to background checks, nor how many currently unregistered gun sellers would have to obtain a license.

Easily reversible by a future president, the government's guidance to gun sellers lacks the legal oomph of a new law, such as the one Obama and likeminded lawmakers tried but failed to pass in 2013. The Justice Department said online the guidance "has no regulatory effect and is not intended to create or confer any rights, privileges, or benefits in any matter, case, or proceeding."

What's more, none of the steps would have probably prevented any of the recent mass shootings that Obama invoked in the East Room: Aurora, Oak Creek, Charleston, Newtown, to name some. But Obama defiantly rejected that critique, dismissing it as the tired trope of gun lobbyists who question "why bother trying?"

"I reject that thinking," Obama said. "We maybe can't save everybody, but we could save some."

AP Review of recent mass shootings

The gun control measures a tearful President Barack Obama announced Tuesday would not have prevented the slaughters of 20 first-graders at Sandy Hook Elementary School in Newtown, Connecticut, or 14 county workers at a holiday party in San Bernardino, California.

Obama's executive action expands mandatory background checks to gun shows, flea markets and online sales, adds more than 230 examiners and staff to help process them and calls on states to submit accurate and updated criminal history data.

In Aurora, Colorado, and at the Navy Yard in Washington, D.C., men undergoing mental health treatment were cleared to buy weapons because federal background checks looked to criminal histories and court-ordered commitments for signs of mental illness. The Obama administration is making changes in that realm by seeking to plug certain Social Security Administration data into the background check system and by helping states report more information about people barred from gun possession for mental health reasons.

The suspect in a shooting at a church in Charleston, South Carolina, should have been flagged at the time, but errors and delays cleared the way for his purchase.

Though the moves probably wouldn't have prevented recent mass shootings, Obama rejected the idea that undermines the changes.

"We maybe can't save everybody, but we could save some," Obama said.

A look at how some recent mass shooting suspects got their weapons:

Dec. 2, 2015, San Bernardino, California, 14 killed

Syed Farook and his wife used weapons that the FBI says his neighbor, Enrique Marquez, purchased legally from a federally licensed dealer in 2011 and 2012. Marquez, now facing conspiracy and other charges, told investigators that Farook asked him to purchase the weapons because he would draw less attention. At the time, the FBI says, the men were plotting to shoot up a community college and a highway.

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Oct. 1, 2015, Roseburg, Oregon, 10 killed

Christopher Harper-Mercer and his family members legally purchased the handguns and rifle he used in the Umpqua Community College shooting from a federally licensed gun dealer, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

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July 16, 2015, Chattanooga, Tennessee, 5 killed

The FBI says some of the weapons Muhammad Youssef Abdulazeez used in his attack on a pair of military facilities were purchased legally and some were not. It is unclear when the purchases were made and whether he was subject to a background check. Relatives say Abdulazeez had a history of mental illness, made a series of overseas trips and was arrested in April on suspicion of driving under the influence of alcohol. In May 2013, he failed a background check for an engineering job at a nuclear power plant in Ohio.

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June 17, 2015, Charleston, South Carolina, 9 killed

A February drug arrest should have prevented Dylann Roof from purchasing the pistol authorities say he used at Emanuel AME Church, but a record-keeping error and background check delay allowed the transaction to go through. The FBI says a background check examiner never saw the arrest report because the wrong arresting agency was listed in state criminal history records. After three days passed, the gun dealer was legally permitted to complete the transaction.

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Sept. 16, 2013, Washington, D.C., 12 killed

Aaron Alexis, a former reservist turned civilian contractor, passed state and federal background checks and legally purchased the pump-action shotgun used in the Washington Navy Yard shooting despite a history of violent outbursts and recent mental health treatment. Alexis was accused of firing a gun in anger in Texas in 2004 and Seattle in 2010, but was not prosecuted in either case. In 2011, he received an honorable discharge despite bouts of insubordination, disorderly conduct and unauthorized absences. None of that would have disqualified him from purchasing a weapon.

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Dec. 14, 2012, Newtown, Connecticut, 26 killed

Adam Lanza used his mother's weapons, including a .223-caliber semi-automatic rifle, in the massacre at Sandy Hook Elementary School. Investigators say Lanza's mother, whom he fatally shot before going to the school, also purchased the ammunition.

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July 20, 2012, Aurora, Colorado, 12 killed

James Holmes was receiving psychiatric treatment when he passed required federal background checks and legally purchased the weapons he used in the movie theater assault. As in the Navy Yard case, Holmes' treatment alone would not have disqualified his purchases. They would have been blocked if had he been adjudicated as a mental defective or committed to a mental institution.

U.S. Gun Sales in 4 charts

Data curated by FindTheData