WASHINGTON (AP) — Just a year ago, President Joe Biden signed the first significant piece of federal gun safety legislation in nearly three decades.

It was a good start, Biden has said, but it didn't go far enough.

On Friday, the Democratic president will speak at a summit in Connecticut highlighting how the sweeping law has been implemented so far. He'll also use it as a moment to push for universal background checks and the banning of so-called "assault weapons." Those are part of a 2024 political platform that was unthinkable to Democrats as recently as Barack Obama's term.

The gathering is being led by U.S. Sen. Chris Murphy, D-Conn., and major gun safety groups hoping to build on recent progress.

"We actually had it wrong for a long time. We left an opportunity on the table for decades," Murphy said of the push for gun safety legislation.

Even before the Sandy Hook massacre in Murphy's state in 2012 spurred him to action, there was a mythology around Democratic election losses that dogged the party following passage of a crime bill in the 1990s — that voters weren't interested in gun safety and it was a losing issue politically. "That was just a lie," Murphy said. "But it was a lie the gun lobby did a great job of selling, with some help from Democrats."

Last year's law, signed just weeks after a mass shooting that killed 19 elementary school children and two teachers in Uvalde, 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 for authorities to take weapons away from people adjudged to be dangerous.

There's been success: Stepped-up FBI background checks have blocked more than 200 transactions of attempted purchasers under the age of 21. Prosecutions have increased for unlicensed gun sellers, and new gun trafficking penalties have been charged in more than 100 cases around the country. Prosecutions for those who sell firearms without a license doubled.

Millions of new dollars have flowed into mental health services for children and schools. On Friday, the departments of Health and Human Services and Education sent a joint letter to governors highlighting resources available to them to help support mental health — in particular if a student has been impacted by gun violence.

"I think there's no question about it, the passage was a watershed moment," said John Feinblatt, head of Everytown for Gun Safety. The law "clearly broke a log jam."

"What we're really going to do is continue to build on the moment both at the federal and the state level," he said.

Yet since that bill signing last summer, the tally of mass shootings in the United States has only grown. As of Friday, there have been at least 26 mass killings in the U.S. so far in 2023, leaving at least 131 people dead, not including perpetrators who died, according to a database maintained by The Associated Press and USA Today in partnership with Northeastern University.

That puts the country on a faster pace for mass killings than in any other year since 2006, according to the database, which defines a mass killing as one in which four or more people are killed, not including the perpetrator, within a 24-hour period.

Firearms are the No. 1 killer of children in the U.S., and so far this year 85 children younger than 11 have died by guns and 491 between the ages of 12 and 17 have died. As of 2020, the firearm mortality rate for those under age 19 is 5.6 per 100,000. The next comparable is Canada, with 0.08 deaths per 100,000.

"Too many schools, too many everyday places have become killing fields in communities across America. And in each place, we hear the same message: 'Do something. For God's sake, just do something,'" Biden said on the anniversary of the Uvalde shooting. "We did something afterwards, but not nearly enough."

The president has said he'd like to ban so-called "assault weapons," a political term to describe guns most often used in mass shootings with the capacity to kill a lot of people quickly. Still, the idea of further action — or unilateral action by the White House — makes some Republicans who voted for the 2022 gun legislation uneasy.

"I'm a little apprehensive," said Sen. John Cornyn, R-Texas. "I don't want them writing a rule that basically deviates from what we've negotiated or voted on."

After his speech in West Hartford, Biden will head to a fundraiser in tony Greenwich. In the coming days, he will accelerate his campaign travel, making stops in New York, California, Illinois and Maryland before the end of the month.

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Associated Press writer Mary Clare Jalonick contributed to this report.