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, 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.
An emotional president employed all of his rhetorical skill to justify what are, in reality, executive actions that only modestly expand federal regulation of firearm sales.
Standing in a room filled with victims of gun violence, he explained that the murder of schoolchildren in Newtown, Connecticut, changed him - and that he hoped it would change the country.
Three years have passed since that school massacre, however, and the country hasn't changed. While some states have toughened their laws, others have expanded gun rights and the US Congress has taken no action.
So Mr Obama did what he could, and wrapped the move in language that sounded more appropriate for a ceremony announcing the passage of sweeping legislation that, in today's political environment, has no chance of reaching his presidential desk.
And even this small move will likely be fiercely challenged in court, in Congress and at the ballot box by whichever Republican wins the nomination fight to replace him in 2017.