US President weeps as he remembers children killed in mass shooting

President Barack Obama on Tuesday described new steps his administration will take to tighten gun rules and urged Americans to vote for candidates who do more to prevent gun violence, wiping back tears as he remembered children who died in a mass shooting.

As Obama delivered a powerful address in the White House, surrounded by family members of people killed in shootings, his voice rose to a yell as he said the constitutional rights of Americans to bear arms needed to be balanced by the right to worship, gather peacefully and live their lives.

Obama has often said his toughest time in office was grappling with the December 2012 massacre of 20 children and six adults at an elementary school in Newtown, Connecticut.

"Every time I think about those kids, it gets me mad," Obama said, tears rolling down his cheek.

"That changed me, that day," he said, after being introduced by Mark Barden, whose 7-year-old son was killed in the shooting. "My hope earnestly has been that it would change the country."

After that tragedy, the Democratic president failed to persuade Congress to toughen U.S. gun laws. He has blamed lawmakers for being in the thrall of the powerful National Rifle Association gun lobby group.

He said Americans need to be "just as passionate" as the NRA in changing gun laws, but acknowledged it won't happen during his final year in office.

Obama laid out executive action he is taking to require more gun sellers to get licenses and more gun buyers to undergo background checks.

Under the changes, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) will issue guidelines intended to narrow exceptions to a system that requires sellers to check with the Federal Bureau of Investigation to determine whether buyers have criminal records, are charged with crimes or have mental health conditions that would bar them from owning a gun.

Any changes to gun rules in America are fraught with political risk. The U.S. Constitution's 2nd Amendment gives Americans the right to have arms, a right that is fiercely defended.

The stocks of gunmakers Smith & Wesson Holding Corp and Sturm Ruger & Co Inc have climbed since the announcement. On Tuesday morning, Smith & Wesson jumped was up 10 percent to $25.58 a share and Sturm Ruger was up more than 6 percent at $65.46.

Legal challenges to the changes are expected and Republican presidential candidates have promised to reverse his order if they win the White House. But Obama, entering his eighth and last year in office, has said his measures are within his authority and consistent with the Constitution.