Democratic presidential hopeful Martin O'Malley unveiled his proposal for reducing an "epidemic and sickness" of gun violence Monday at a Manhattan roundtable that included mothers who had lost sons in gun-related incidents.

"There is no other advanced nation . . . that buries as many of our sons and daughters from gun violence quite so much as the United States of America does," O'Malley said.

The former governor of Maryland said as president, he would aim to reduce the number of gun deaths -- homicides, suicides and accidents -- by half by 2025. O'Malley's plan includes a national firearms registry, revoking licenses when gun dealers break the law, an end to unregulated Internet gun sales, information-sharing between states and new safety standards for government-purchased firearms.

O'Malley, who championed gun safety regulations as governor of Maryland and mayor of Baltimore, spoke at the Boys & Girls Harbor learning center in East Harlem.

He is trailing badly among Democrats eyeing the White House in the 2016 race.

An ABC News/Washington Post poll Monday showed him in fourth place with 2 percent of the vote, behind Hillary Rodham Clinton, Bernie Sanders and Joe Biden, who has not declared his candidacy.

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Jackie Rowe-Adams, of Harlem Mothers S.A.V.E. -- or Stop Another Violent End -- said Monday that she appreciated O'Malley's contribution to the national conversation. Rowe-Adams lost two of her sons, ages 17 and 28, in gun-related incidents.

"We can't bring back our kids. . . . But we can certainly, certainly try to help another mother and another father and another family from hurting and feeling the pain that we are," she said at the roundtable.

Leah Gunn Barrett, of New Yorkers Against Gun Violence, said New York has strong gun laws, but illegal firearms still make their way in via Virginia and elsewhere like "pollution or cockroaches."

Representatives of the National Rifle Association did not respond Monday to a request for comment on O'Malley's proposal.

But the Democratic candidate is featured on the cover of this month's NRA publication, "America's 1st Freedom," alongside the headline "Menace in the Second," a nod to the Second Amendment.

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O'Malley impressed some participants of the roundtable, but he didn't secure their support.

Rowe-Adams and Juanita Morgan, who also had two sons who were killed, said they were still undecided on whom to back in 2016.