Senate aides say a Democratic and a Republican senator are working on a compromise expanding required federal background checks to gun shows and to online firearms sales.
If an agreement could be completed, it could represent a significant breakthrough in the effort by President Barack Obama and his allies to restrict guns in the wake of the mass shooting at an elementary school in Newtown, Conn., that killed 26 first-graders and staff last December.
The aides said the potential deal is being worked on by Democratic Sen. Joe Manchin of West Virginia and Republican Sen. Pat Toomey of Pennsylvania. Manchin is a moderate with an A rating from the National Rifle Association, while Toomey has solid conservative credentials.
The aides spoke on condition of anonymity to disclose private negotiations.