WASHINGTON — The Biden administration is proposing a rule that would require thousands more firearms dealers to run background checks, in an effort to combat rising gun violence nationwide.

The proposal comes after a mandate from President Biden to find ways to strengthen background checks following the passage of bipartisan legislation on guns last year.

People who sell firearms online or at gun shows would be required to be licensed and run background checks on the buyers before the sale under the rule proposed by the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The bureau estimates that the rule would affect anywhere from 24,500 to 328,000 sellers. It is aimed at those who are in the business of gun sales, rather than those with personal collections.

Background checks help prevent guns from being sold to people convicted of crimes, teenagers, and others who are legally blocked from owning them, said the agency’s director, Steve Dettelbach. Federally licensed firearm dealers are also required to keep records and sell guns with serial numbers, both of which help law enforcement trace weapons used in crimes.

“Unlicensed dealers sell guns without running background checks, without keeping records, without observing the other crucial public safety requirements by which the (federally licensed firearm dealer) community abides,” he said.

Attorney General Merrick Garland said Congress passed the gun legislation to reduce gun violence, including by expanding background checks, and said the new rule implements that mandate.

Overall, stricter gun laws are desired by a majority of Americans and in particular background checks, regardless of what the current gun laws are in their state, according to a recent AP-NORC poll on guns. That desire could be tied to some Americans’ perceived impact of what fewer guns could mean for the country — namely, fewer mass shootings. As of Monday, there have been at least 33 mass killings in the U.S. so far in 2023, leaving at least 163 people dead, not including shooters who died, according to a database maintained by the AP and USA Today in partnership with Northeastern University.

Over the weekend, three Black people were shot to death by a white man wearing a mask and firing a weapon emblazoned with a swastika in Jacksonville, Florida. The shooter, who had purchased the weapons legally despite previously being involuntarily committed for a mental health exam, killed himself.

The legislation last year Congress passed was the most comprehensive gun control in 30 years and it followed a deadly mass shooting in a Uvalde, Texas, elementary school.

The 2022 law toughened background checks for the youngest gun buyers, sought to keep firearms from domestic violence offenders, and aimed to help states put in place red flag laws that make it easier to take weapons away from people judged to be dangerous.

Biden has said the law doesn’t go far enough. White House Press Secretary Karine Jean-Pierre said Thursday the administration would continue to push for more gun control.

“This administration will do everything it can to combat the epidemic of gun violence that is tearing up our families, our communities, and also our country apart,” she said.

The Giffords Center to Prevent Gun Violence applauded the proposed rule change, saying it closes a “gaping loophole.” Executive Director Peter Ambler said the Biden administration had taken a “giant step forward towards our goal of universal background checks.”

Kris Brown, president of the gun control group Brady, said more than 1 in 5 gun sales in the U.S. are conducted without a background check.

Gun rights groups, on the other hand, have argued it would do little to stop the gun violence problem. Those advocates have previously quickly sued over other ATF rule changes that they argue infringe on gun rights.

The proposed rule will be open for public comment for 90 days. It was not immediately clear when it might become final.