The shootings in May - one at a Texas elementary school that killed 19 young children and two teachers, and another at a New York supermarket that left 10 Black people dead - have piled pressure on politicians to take action.
Republicans lawmakers, who have repeatedly blocked tougher measures, are still resisting major changes to gun regulations, instead pointing to mental health issues as the root of the problem.
But the new framework notably has backing from at least 10 Republicans, meaning it has a strong chance of earning the supermajority of 60 votes needed to advance in the 100-seat US Senate.
The reforms include tougher background checks for gun buyers under 21, increasing resources for states to keep weapons out of the hands of people deemed a risk, and adding domestic violence convictions and restraining orders to the national background check database.
“Today, we are announcing a commonsense, bipartisan proposal to protect America’s children, keep our schools safe, and reduce the threat of violence across our country,” the group of 20 lawmakers said in a statement.
“Our plan increases needed mental health resources, improves school safety and support for students, and helps ensure dangerous criminals and those who are adjudicated as mentally ill can’t purchase weapons.”
President Joe Biden praised the proposals and urged lawmakers to quickly turn them into legislation, while saying the measures do not go far enough.
“Obviously, it does not do everything that I think is needed, but it reflects important steps in the right direction, and would be the most significant gun safety legislation to pass Congress in decades,” he said in a statement.
“With bipartisan support, there are no excuses for delay, and no reason why it should not quickly move through the Senate and the House.”
Both Chuck Schumer and Mitch McConnell - the top Democrat and Republican in the Senate - expressed support for the bipartisan effort, signaling that legislation based on the proposals could make it through the upper house.
Frequent mass shootings
Biden had pushed for more substantive reforms, including a ban on assault rifles - which were used in both the Texas and New York shootings - or at least an increase in the age at which they can be purchased.
He had also urged lawmakers to ban high-capacity magazines, mandate safe storage of firearms, and allow gun manufacturers to be held liable for crimes committed with their products.
The Democrat-controlled House of Representatives passed a broad package of proposals this month that included raising the purchasing age for most semi-automatic rifles from 18 to 21.
But the party does not have the requisite 60 votes to advance it in the Senate, leaving the bipartisan deal as the only hope for federal legislation to address firearms violence.
House Speaker Nancy Pelosi welcomed the Senate agreement, saying that while more is needed, including universal background checks and bans on high-capacity magazines, “this package will take steps to save lives.”
Frequent mass shootings have led to widespread outrage in the United States, where a majority of people support tighter gun laws, but opposition from many Republican lawmakers and voters has long been a hurdle to major changes.
A strong opponent of tougher measures is the National Rifle Association, which has been weakened by scandals and was hit by a lawsuit from New York state’s attorney general, but still wields considerable influence.
“The media, leftist politicians, and gun-hating activists are bullying NRA members and gun owners because they want us to give up. We won’t bend a knee,” the lobby tweeted on Saturday.
That day, thousands of people took to the streets across America to push for action on gun violence, which has killed more than 19,400 people in the country so far this year, more than half of them suicides, according to the Gun Violence Archive.
“The will of the American people is being subverted by a minority,” 63-year-old protester Cynthia Martins said during a demonstration Saturday in Washington.
“Hand wringing is not going to do anything - you have to make your voice heard.”