Two US senators have brokered a bipartisan deal to expand background checks on gun buyers, boosting White House hopes for a firearms control law.
Senator Joe Manchin, a Democrat, and Senator Pat Toomey, a Republican, unveiled their plans in Washington DC.
The proposal would expand criminal background checks for buyers to include gun shows and online sales.
President Barack Obama has been calling for gun controls since a massacre at a school in Connecticut in December.
"Today is just the start of a healthy debate that must end with the Senate and House hopefully passing these common sense measures and the president signing them into law," Sen Manchin told reporters on Wednesday.
'Not a cure-all'
He said Democratic Majority Leader Harry Reid had assured them their plan would be considered as the first amendment to a wider bill.
On Thursday, the Senate plans to vote on whether to begin debate on Democratic-led legislation that would expand background checks to virtually all gun sales, make gun-trafficking a felony, and boost funding for school safety.
The Manchin-Toomey plan is stricter than the current law, which requires checks only when guns are bought through a licensed dealer and thus exempts private sales, many sales at gun shows, and some online sales. But it is viewed as narrower than congressional Democrats' proposals.
Sales among friends or family members would be exempt from the background-check requirement, under the two senators' proposal.
Sen Toomey, a Republican from Pennsylvania, said he did not believe expanding background checks to block illegal buyers amounted to gun control.
"[Checks] are not a cure-all, but they can be helpful," the senator said, adding that 1.8 million firearms sales have been blocked by the current system.
The plan has also won the backing of New York Democratic Senator Charles Schumer, who attempted to broker an earlier compromise, and of a group lobbying for stricter gun controls founded by New York City Mayor Michael Bloomberg.
"Our bipartisan coalition of more than 900 mayors strongly supports this bill," Mr Bloomberg, an independent, said in a statement.
Michelle Obama in Chicago
Also in the agreement is a plan to establish a federal commission on mass violence that would seek the expertise of those in the fields of mental health, school safety, firearms and entertainment.
The Senate's Democratic leadership believes it now has enough Republican support to thwart a conservative attempt to stop the bill even being considered on the floor of the chamber.
In a statement, the National Rifle Association said that more background checks "will not prevent the next shooting, will not solve violent crime and will not keep our kids safe in schools".
Sen Manchin said he and Sen Toomey had been in touch with multiple groups during their discussions, including the NRA.
And a White House spokesman confirmed that Mr Obama had called negotiators from both parties on Tuesday.
The White House will continue its campaign on Wednesday as First Lady Michelle Obama visits a Chicago high school where 29 current or former students have been shot in the past year.
Relatives of those killed in the December school massacre at Newtown, Connecticut, lobbied lawmakers on Tuesday. The family members were whisked to Washington by Mr Obama aboard Air Force One.
"People should listen to what we have to say and move the debate forward," said Mark Barden, who lost his seven-year-old son, Daniel at Sandy Hook Elementary School.
"It's not just about our tragedy. Lots of kids are killed every day in this nation. We have to help lead the change."
White House calls for a ban on assault weapons and a limit on the capacity of ammunition magazines have not gained traction in Congress.