An emotional US President Barack Obama has unveiled new restrictions on gun purchases, saying the "constant excuses for inaction" have to stop.
Wiping away tears, the president recalled the Sandy Hook primary school shooting in 2012 where 20 children and six adults were killed.
His executive actions, without Congress approval, widen background checks on potential gun buyers.
But the National Rifle Association said it would fight Mr Obama's measures.
And the leader of the House of Representatives, the Republican Paul Ryan, said the plans were certain to be challenged in the courts.
"His words and actions amount to a form of intimidation that undermines liberty," he said.
Meanwhile, sales of guns in the US appear to have risen, amid speculation in recent weeks that the White House was going to tighten the law.
Earlier, the president announced the law change at the White House, while surrounded by survivors and relatives of victims of shootings.
"The gun lobby may be holding Congress hostage right now, but they can't hold America hostage," Mr Obama said.