The bipartisan deal on expanded background checks for gun buyers appeared Sunday to garner more Republican support, but Capitol Hill leaders could not say whether the overall gun-control bill will have enough votes as the full debate begins this week.

The legislation will need 60 votes to pass in the chamber, which means it will need Republican support as well as support from Senate Democrats facing re-election in districts with a strong tradition of gun rights.

“It’s an open question as to whether or not we have the votes,” Pennsylvania Republican Sen. Pat Toomey told CNN’s “State of the Union.” “I think it’s going to be close.”

Toomey joined West Virginia Democratic Sen. Joe Manchin in crafting the background proposal, which would cover Internet and gun show purchases but would still exempt sales between family members.