Wiping back tears as he remembered children who died in a mass shooting, President Barack Obama has described new steps he is taking to tighten gun rules and urged Americans to vote for candidates willing to do more to prevent gun violence.

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.

"Every time I think about those kids, it gets me mad."

Obama has often said his toughest time in office was grappling with the December 2012 massacre of 20 children and six adults at a primary 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 US gun laws. He has blamed lawmakers for being in the thrall of the powerful National Rifle Association gun lobby group.

The stocks of gunmakers Smith & Wesson Holding Corp and Sturm Ruger & Co Inc have climbed since the announcement. On Tuesday, Smith & Wesson jumped 12 per cent to $US26.10 ($A36.34) a share and Sturm Ruger was up nearly 7 per cent at $US65.62.

Obama acknowledged that laws won't change during his remaining year in office, but said he will continue to raise the issue in the time he has left.

The US Constitution's 2nd Amendment gives Americans the right to have arms, a right that is fiercely defended.

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

Under the changes, the US Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is issuing 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.

The proposal is "ripe for abuse" by the government, said Chris Cox, an official with the National Rifle Association in a statement, adding that the powerful gun lobby group will continue to fight to protect Americans' constitutional rights.

Legal challenges to the changes, which are contained in guidance from the ATF, are expected.

The crucial question in any direct legal challenge will be whether the ATF guidance creates new obligations, or merely clarifies existing law.

The more the Obama administration acts as though the guidance has created a new legal requirement, the more legal trouble it might invite, said Lisa Heinzerling, administrative law professor at Georgetown University.

Republican leaders were quick to denounce Obama's gun changes, with most Republican candidates for the 2016 presidential race promising to reverse his actions if they win the White House.