Lawmakers in the state of Connecticut will vote on a sweeping set of gun restrictions, including a ban on new high-capacity magazines.
The proposal requires background checks on all gun sales and expands the state's assault weapons ban.
It comes as new federal gun measures appear to have stalled in Congress.
Debate over US gun laws was reignited after a gunman killed 26 people, including 20 children, at a Connecticut primary school in December.
Tighter gun restrictions also passed in New York and Colorado in the wake of the shooting.
On Monday, six relatives of children and a school staff member killed at Sandy Hook Elementary School in December travelled to the state capitol of Hartford to call for a complete ban on high-capacity ammunition magazines, several of which the gunman used in that attack.
The new proposal, made public after weeks of negotiation by legislative leaders, is expected to go to a vote on Wednesday with the support of both Democrats and Republicans.
Senate Minority Leader John McKinney, a Republican whose district includes Newtown, called the proposal "the most comprehensive package in the country because of its breadth".
It would create a registry of weapons offenders and require a new state eligibility certificate for the purchase a rifle, shotgun or ammunition.
Such a certificate would be issued after the buyer was fingerprinted, took a firearms training course and passed both a criminal background check and checks to see whether the person had been committed to a psychiatric hospital.
Criminal background checks would now be required of all prospective gun purchasers. Currently, federal law exempts so-called private transactions, which can include online sales and sales at gun shows.
In addition to proposals directly related to guns, Mr McKinney said there was also "a lot here underneath the surface" addressing mental health, school security and other issues.
In a compromise, legislators did not ban existing ammunition magazines of more than 10 rounds. Instead, already purchased high-capacity magazines will have to be registered.
'Mandatory' gun ownership
Some Newtown parents criticised the compromise.
"It doesn't prevent someone from going out of the state to purchase them and then bring them back," said Mark Barden, whose seven-year-old son Daniel was killed in the shooting.
Jake McGuigan, a spokesman for the Newtown-based gun group National Shooting Sports Foundation, also questioned the magazine registry.
"How will they register a magazine?" he told the Associated Press. "It seems a little weird.''
There was outrage in recent days after Newtown residents received robocalls from the National Rifle Association, a powerful lobby group, urging them to oppose the gun control bill.
The US Congress is expected to vote on a raft of gun proposals this month, including broadened background checks. Gun rights advocates have pledged to block the measures.
On Monday, Connecticut House Speaker Brendan Sharkey, a Democrat, said the state was showing Washington "the way to get this job done".
Also on Monday, a small Georgia town approved a symbolic measure mandating gun ownership.
City officials in Nelson, a town of 1,300 north of Atlanta, say the law, called the Family Protection Ordinance, makes a statement about gun rights during a national conversation about firearm regulations.
The measure exempts convicted felons barred by federal law from gun ownership, those with physical and mental disabilities, and anyone who objects to owning a gun. There will be no penalty for non-compliance.