With Congress grappling over gun legislation, Vice President Joe Biden vowed to continue fighting for a ban on semi-automatic firearms modeled after military assault weapons, despite its bleak future on Capitol Hill.

"I am still pushing that it pass," Biden said Wednesday on NPR. "We are still pushing that it pass."

His words echoed similar refrains made by Sen. Dianne Feinstein, who spearheaded the assault weapons ban in this Congress. The California Democrat pledged not to "lay down and play dead" amid calls to keep the ban out of a larger gun package.

The ban, categorically opposed by the National Rifle Association, would get fewer than 40 votes, Senate Majority Leader Harry Reid said Tuesday, far below the threshold needed to defeat a filibuster or pass the Senate.

Instead, Feinstein could propose the ban as an amendment to the gun legislation on the Senate floor in order to get a vote on it, Reid said.

"The same thing was told to me when the first assault weapons ban in 1994 was attached to the Biden crime bill," Biden said. "That it couldn't possibly pass. It was declared dead several times."

The bill eventually passed and remained law until 2004, when it expired. Feinstein was also a key player in that legislation.

In the wake of the Newtown elementary school shooting, President Barack Obama and Biden made a series of proposals to combat gun violence, including an assault weapons ban and a limit to ammunition feeding devices.

"Attitudes are changing and I think the president and I are going to continue to push and we haven't given up on it," Biden said Wednesday.

The vice president will appear at an event Thursday in New York with Mayor Michael Bloomberg and Newtown families in an attempt to push new federal gun laws, as debate nears in the Senate and some key provisions struggle for support.