The president unveiled new rules on “ghost guns” — firearms that are assembled at home, which lack serial numbers and are harder to track — among other moves designed to make it harder for unqualified people to obtain dangerous weapons.

Biden also announced David Chipman as his pick to run the Bureau of Alcohol, Tobacco, Firearms and Explosives, although it is unclear how the nominee will fare in an evenly divided Senate. Chipman is a former ATF agent and now a senior adviser to a gun-control group founded by former congresswoman Gabrielle Giffords (D-Ariz.), who was severely injured in a mass shooting in 2011.

Biden said his moves Thursday do not relieve Congress of the responsibility to act. He urged lawmakers to take up gun-control legislation, including measures already passed by the House that would require more gun buyers to undergo background checks.

“They’ve offered plenty of thoughts and prayers, members of Congress, but they’ve passed not a single new federal law to reduce gun violence,” Biden said. “Enough prayers. Time for some action.”

Vice President Harris, a former prosecutor, also urged Congress to pass long-stalled gun measures. “What are we waiting for?” Harris said. “Because we aren’t waiting for a tragedy. I know that we’ve had more tragedy than we can bear.”

Biden’s moves came amid a growing impatience from gun-control activists that the administration has not acted more quickly. Biden promised during his campaign that he would take action to limit gun violence on the first day of his administration, but that fell by the wayside.

Biden has prioritized other issues in the early going, including coronavirus response and economic aid. He suggested recently that he considers gun control less urgent than those immediate crises, one that can be tackled over the long term.

But the issue of gun violence moved vividly the forefront after the two mass shootings, one in Georgia in which eight people died, and another in Colorado, where 10 were killed.

Biden was joined in the Rose Garden by first lady Jill Biden and a number of longtime gun-control advocates, including Giffords, who became a leading anti-gun activist after she survived a mass shooting outside a supermarket. Her husband, Mark Kelly, is now a senator from Arizona.

After giving his remarks, Biden bounded offstage and offered Giffords an elbow bump. “I wasn’t supposed to do that,” the president said.

Biden laid out several ways his administration will tackle gun violence. He ordered action on ghost guns, firearms without serial numbers that are sold in kits. He directed the Justice Department to draft a new rule regulating a device that can be placed on a pistol to turn it into a short-barreled rifle.

He also instructed the Justice Department to create a template that states can use to enact “red flag” laws, which allow judges to seize firearms from people who are deemed a threat to themselves or others. And he ordered a repeat of a landmark 2000 gun-trafficking study that was instrumental in helping police determine the source of guns used in crimes.

Gun activists said they were pleased. “The president did a really great job here looking at the many, many forms of gun violence and addressing those,” said Brian Lemek, executive director of Brady PAC, a gun-control group. “We knew he would come through.”

Some said Biden’s willingness to use the bully pulpit to focus on gun control was perhaps the most meaningful aspect of Thursday’s event.

“You need the president pushing,” said Paul Helmke, former president of the Brady Campaign, adding that Biden’s rhetoric on gun control is far stronger than President Barack Obama’s initial approach to the issue.

Biden, a former chairman of the Senate Judiciary Committee, has a record of supporting gun-control initiatives, including the 10-year assault weapons ban that was part of a 1994 crime bill he sponsored.

But the politics of gun control have always been turbulent. Rural voters, who skew sharply Republican, strongly support gun rights, while Democratic-leaning city dwellers often oppose them. The suburbanites coveted by both parties have tended to be more open to gun control recently.

Democrats used to shy away from talking about the subject, but a spate of mass shootings in recent years created a new set of young activists, making gun violence a bigger subject on the campaign trail. Both parties are using the issue to motivate their base to vote, a big shift from a decade ago, when Democrats were wary of the issue and believed it had contributed to some of their election losses.

Even now, Biden faces an uphill struggle to pass any new gun laws. The 50-50 Senate means that 10 Republicans would need to join all Democrats to pass gun restrictions, since 60 votes are needed to pass most bills in the Senate.

The country’s largest pro-gun lobby, the National Rifle Association, is mired in multiple legal battles, but it remains influential among Republicans. On Thursday, NRA officials referred to Biden’s Rose Garden event as a “circus” on their official Twitter account and outlined their opposition to his moves.

“These actions could require Americans to surrender lawful property, push states to expand confiscation orders, and put a gun control lobbyist to head ATF,” the officials said. “Biden is dismantling the 2nd Amendment.”

Anticipating this argument, Biden insisted that his moves are constitutional. “The idea is just bizarre to suggest that some of the things we’re recommending are contrary to the Constitution,” Biden said.

Sen. Richard Blumenthal (D-Conn.), who attended Thursday’s event, noted that Attorney General Merrick Garland recently served as chief judge of the U.S. Court of Appeals for the D.C. Circuit, which hears legal challenges to federal regulations.

That leaves Garland well equipped to draft the new Justice Department regulations in a way that would allow them to survive court challenges, Blumenthal said. “If you had to pick someone who knows about the importance of dotting the i’s and crossing the t’s when it comes to rulemaking, Merrick Garland would be your first choice,” he added.

Garland himself signaled Thursday he takes the issue seriously.

“We stand here today, not at a moment of tragedy, but in the midst of enduring tragedy,” the attorney general said. “I know that the Department of Justice alone cannot solve the problem. . . . But there is work for the department to do, and we intend to do it.”

Activists applauded the nomination of Chipman, especially since Biden has generally avoided tapping activists to fill key roles.

“He knows and understands guns and the gun violence prevention movement and the many avenues for individuals who are prohibited from having guns to get them,” Lemek said.

One surprise was that Biden opted not to use his executive authority to erode the liability shield enjoyed by gun manufacturers, a step he had pledged to take as a candidate. Instead he urged Congress to remove the shield.

“Imagine how different it would be had that same exemption been available to tobacco companies, who knew and lied about the danger they were causing, the cancer caused and the like,” Biden said.

He added: “If I get one thing on my list — the Lord came down and said, ‘Joe, you get one of these’ — give me that one.”

White House press secretary Jen Psaki, asked why it had taken more than 70 days for the president to address the liability issue, replied, “There’s no holdup. It’s just, legislation needs to be reintroduced.”

Biden signaled that he’s not expecting results from Congress anytime soon.

“We’ve got a long way to go,” Biden said. “It seems like we always have a long way to go.”

Anne Gearan and Seung Min Kim contributed to this report.