WASHINGTON • US President Donald Trump - under pressure from angry, grieving students from a Florida high school where a gunman killed 17 people last week - has ordered the Justice Department to issue regulations banning "bump stocks".
The devices convert semi-automatic guns into automatic weapons like those used last year in the massacre of concert-goers in Las Vegas.
He had earlier signalled he was open to supporting legislation that would modestly improve the gun background check system.
But Mr Trump's first embrace as United States president of any gun control measures was dismissed as minor by gun control supporters. The National Rifle Association (NRA) already supports the background check legislation and also backs bump stock regulation, but not an outright ban.
Speaking at the White House on Tuesday, days after the shooting at Marjory Stoneman Douglas High School, Mr Trump said he had directed Attorney-General Jeff Sessions to develop the regulations.
"We cannot merely take actions that make us feel like we are making a difference," he said. "We must actually make a difference."
In Florida, meanwhile, the Republican-controlled state House on Tuesday rejected an effort to immediately consider a Bill to ban large-capacity magazines and the type of assault rifles used in last week's attack, even as students from Stoneman Douglas High School watched from the gallery.
WALK THE TALK
We cannot merely take actions that make us feel like we are making a difference... We must actually make a difference.
PRESIDENT DONALD TRUMP, speaking at the White House days after a shooting at Marjory Stoneman Douglas High School.
White House spokesman Sarah Huckabee Sanders said President Trump was determined to find ways to protect Americans, especially children, from gunmen. Asked about a broader ban on assault weapons, she said the White House has not "closed the door on any front".
Despite the day's developments, there was deep scepticism in Washington that anything would change because of the long history of inaction by state and federal politicians after similar mass shootings.
Gun control activists said they were bracing themselves for another disappointing battle with lawmakers.
Mr Trump, they noted, promised unwavering fealty last year to the NRA, drawing thunderous applause at its annual convention by declaring: "To the NRA, I can proudly say I will never, ever let you down."
The group had endorsed Mr Trump and spent US$30 million on his presidential campaign.
Democratic Senator Chris Murphy, who sponsored the latest background check measure with Republican Senator John Cornyn, said he was unimpressed by Mr Trump's openness to it.
"Let's not pretend this is some huge concession on his part," he said. "If this is all the White House is willing to do to address gun violence, it's wholly insufficient."
The background check Bill, which seeks to improve the existing database used to prevent gun purchases by criminals and the mentally ill, is a small nod in the direction of gun control that does nothing to close loopholes that allow millions of gun sales without a background check. Last year, NRA officials said they were fine with it.
It is also unclear whether Mr Trump's statement of support for the measure, which included a desire for some "revisions", might be linked to other legislation the NRA backs. In the House, a similar background check measure was combined with legislation that would effectively allow people to carry concealed weapons in all 50 states.
That legislation is the top priority for the NRA, and gun control activists have promised to fight it aggressively.
The President's bump stock announcement surprised the Bureau of Alcohol, Tobacco, Firearms and Explosives, which did not appear to have been informed of his pending remarks.