The National Rifle Association is increasing pressure on Washington lawmakers who have endorsed a plan to expand gun background checks.

NRA officials have asked members of the organization to contact their lawmakers to express opposition to the bill. The group has also sent out a mailing for members to specifically call Republican Rep. Mike Hope, who is a police officer previously supported by the NRA.

Hope supports the background check plan, saying Tuesday that it is a reasonable way to help keep guns away from violent criminals and the mentally ill. Hope says he's received about 300 emails related to the gun bill and believes there are a lot of misconceptions about what it does.

Gun buyer already have to undergo a background check if they purchase from a federally licensed firearms dealer. The bill would expand that to sales between private parties.