A bipartisan group of Senate negotiators is expected to announce on Sunday that they have reached a tentative agreement on legislation that would pair modest new gun restrictions with significant new mental health and school security investments — a deal that could put Congress on track to enacting the most significant national response to mass gun violence in decades.

Three people involved in the negotiations confirmed the framework agreement on Sunday, speaking on the condition of anonymity to discuss their status ahead of a formal announcement, which is expected midday Sunday. While significantly weaker than the assault weapons ban, high-capacity ammunition magazine restrictions, and broad background check expansions supported by the majority of Democrats, the gun provisions outlined in the framework could represent the most significant new federal firearms restrictions enacted since the mid-1990s if enacted.

A federal grant program would encourage states to establish “red flag” laws that would allow authorities to keep guns away from people found by a judge to be a potential threat to themselves or others, and federal criminal background checks for gun buyers under 21 would include a mandatory search of juvenile justice records for the first time.

It excludes a proposal supported by President Biden, congressional Democrats, and a few Republicans to raise the minimum age for purchasing at least some rifles from 18 to 21. Handguns already have a federal age limit of 21 and up.

Other provisions could channel billions of dollars in new federal funds into mental health care and school security programs, including funding for new campus infrastructure and armed officers. Several senators said last week that they expected legislation sponsored by Sens. Roy Blunt (R-Mo.) and Debbie Stabenow (D-Mich.) to establish a nationwide network of “community behavioral health clinics” to be a cornerstone of the agreement.

The announcement on Sunday is the result of a hastily launched bipartisan effort launched in the days following the May 24 killing of 19 children and two teachers inside Robb Elementary School in Uvalde, Texas, which came 10 days after another shocking mass shooting inside a Buffalo supermarket.

It also comes just one day after thousands of people attended pro-gun-control rallies across the country organized by the student-led March for Our Lives movement, including one on the National Mall in Washington.

On Sunday, each senator publicly sketched out a general negotiating position.

Murphy, who has led Democrats’ efforts on gun legislation since the 2012 Newtown, Conn., school shooting, said Friday at an anti-gun-violence rally that he was determined to break congressional stasis on gun legislation, but not at any cost: “I’m not interested in doing something unless it’s going to save lives, unless it’s going to be impactful and meaningful.”

Meanwhile, Cornyn, who has an A-plus rating from the National Rifle Association, stated last week that he is open to finding a solution that protects gun owners’ Second Amendment rights.

The following major pitfalls remain: Only a few of the 50 Republican senators were involved in the negotiating group, and under the Senate’s filibuster rule, at least 10 members of the Democratic caucus would have to join with the 50 Republican senators to advance any legislation. Many conservative Republicans have expressed concern about red-flag laws in particular, though negotiators said last week that they believed there would be enough GOP support to pass any deal.

According to those involved in the negotiations, it was unclear how many senators would ultimately sign the statement on Sunday morning. According to one source, there is still hope for at least ten Republicans to sign on, indicating a clear path to passage.

Furthermore, the framework that will be announced on Sunday is merely a statement of principles, not a fully written bill. While people involved in the process said last week that significant portions of the legislation had already been written, new points of contention in Congress frequently arise as the drafting process is completed.

House Speaker Nancy Pelosi (D-Calif.) indicated on Friday that the Democratic-controlled House would move quickly to enact whatever bill the Senate managed to pass. “If it’s life-saving and can make a difference, and they have bipartisan support for it, then we would welcome it,” she said at a news conference.