US President Joe Biden and gun safety campaigners have welcomed the breakthrough but said the measures still do not go far enough.
However, Mr Biden has now urged lawmakers to get the deal through Congress quickly.
What is the US gun control agreement?
The deal reached by senate negotiators is a modest breakthrough and offers measured gun curbs and bolstered efforts to improve school safety and mental health programmes.
The compromise would lead to tougher background checks on people under the age of 21 when they purchase a gun.
Salvador Ramos was 18 when he killed 19 students and two teachers at a primary school in Uvalde, Texas.
Many attackers who have committed mass shootings in the US in recent years have been under the age of 21.
The agreement would also offer money to states that implement “red flag” laws – which makes it easier to temporarily take guns from people considered potentially violent.
The laws could also help to bolster school safety and mental health programmes.
Some people who informally sell guns for profit would be required to obtain dealers’ licences.
This would mean that they would have to conduct background checks on buyers.
Convicted domestic abusers who did not live with a former partner – such as an estranged ex-boyfriend – would be barred from buying firearms.
It would also be a crime for a person to legally purchase a weapon for someone who did not qualify for ownership.
What has the reaction been to the agreement?
Mr Biden welcomed the agreement even though it falls short of tougher measures that has long sought.
He said in a statement that the framework “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”.
The US President added that given the bipartisan support “there are no excuses for delay, and no reason why it should not quickly move through the Senate and the House”.
Senate majority leader Chuck Schumer, for the Democrats, said: “[It’s] a good first step to ending the persistent inaction to the gun violence epidemic.”
Senate minority leader Mitch McConnell, for the Republicans, supported the talks but was more restrained in his praise for the agreement.
He praised the negotiators’ work and said he was hoping for a deal that made “significant headway on key issues like mental health and school safety, respects the Second Amendment, earns broad support in the Senate, and makes a difference for our country”.
The agreement was also endorsed by groups that support gun restrictions including Brady, Everytown For Gun Safety and March For Our Lives.
The National Rifle Association said in a statement that it opposes gun control and infringing on people’s “fundamental right to protect themselves and their loved ones”.
However, the group does support strengthening school security, mental health and law enforcement.
Will this agreement become US law?
Supporters hope that this agreement can be made into law rapidly.
Some 20 senators, including 10 Republicans, released a statement calling for the framework’s passage.
This is highly significant because the biggest obstacle the measure would probably face is in the 50-50 Senate, where 10 Republican Party votes will be needed to attain the usual 60-vote threshold for approval.
The group, led by senators Chris Murphy, John Cornyn, Thom Tillis and Krysten Sinema produced the agreement after two weeks of closed-door talks.
Negotiators said the details and legislative language would be written over the coming days.
The spending figures remain undecided, although congressional aides said billions of US dollars would be spent expanding the number of community mental health centres and suicide prevention programmes.
Finalising the agreement might also produce fresh disputes.
Republicans still oppose the more sweeping changes that the Democrats want – including banning assault-style firearms such as the AR-15 which was used in Uvalde.
The last major firearms restrictions made into law was the 1994 assault weapons ban, which Congress let expire 10 years later.