Washington voters may get the final say on whether the state expands background checks on gun sales.

Democratic Rep. Jamie Pedersen of Seattle said Tuesday he plans to add a referendum clause to his bill. He says the move was necessary in order to secure enough votes to pass the measure out of his chamber.

Pedersen says he is confident that supporters of the bill will be able to defend it at the ballot box, even if the National Rifle Association leads an effort to stop it.

The bill would require background checks to cover private gun transactions. Gun buyers currently must undergo a background check when they purchase a weapon from a federally licensed firearms dealer.