WASHINGTON (AP) -- One of the principal sponsors of defeated gun background check legislation says he isn't giving up on getting a bill passed.

West Virginia Democratic Sen. Joe Manchin says backers of expanded background checks for gun purchases must focus on "where the comfort zone is" with gun owners.

A bill Manchin co-sponsored with Republican Sen. Pat Toomey of Pennsylvania failed to clear the Senate last month. The National Rifle Association, which staunchly opposed the measure, celebrated its defeat at a convention in Houston.

Manchin tells "CBS This Morning" in an interview Tuesday that the NRA, of which he is a member, has been "rattling the cage" to stir up opposition to enhanced background checks. He says nothing in the legislation infringes on the 2nd Amendment rights of gun owners.