President Obama and gun control groups back the weapons ban, which expired in 2004. Feinstein said she was "dismayed" at the lack of courage from senators who were voting against gun control measure, which was opposed by the National Rifle Association.

“I believe you should have the right to own a gun,” Reid said on the Senate floor. “But you do not need an assault weapon to defend yourself and your property. Assault weapons have one purpose and one purpose alone, to kill a lot of people very quickly.”

Ahead of the vote, Sen. Chuck GrassleyChuck GrassleyFormer Sen. Bob Dole dies at 98 Alarm grows over smash-and-grab robberies amid holiday season GOP blocks bill to expand gun background checks after Michigan school shooting MORE (R-Iowa) said Feinstein's amendment violated Second Amendment rights.

Democrats have been pushing for stricter gun laws since December, when a gunman killed 20 first-graders and six school employees at Sandy Hook Elementary School in Newtown, Conn.

Feinstein said the Sandy Hook massacre “shocked the conscience of America.”

“Over the years as I’ve watched, I’ve come to see that these weapons are attractive to certain types of people: gun collectors, target shooters, hunters, but death tolls show that there is another group that covets these guns even more … their goal is to kill indiscriminately. … The question is, can this group of people who will kill with these weapons, buy these weapons easily, the answer is yes.”

Feinstein said her amendment had one purpose “to dry up the supply of assault weapons and high capacity firearms.” Her amendment would have banned the future manufacturing, imports and sales of certain assault weapons, but would not have taken the guns away from those who already legally own them.

The Senate was scheduled to vote on nine amendments Wednesday, all of which were subject to a 60-vote threshold. More amendment agreements are possible later this week.