The narrow margin underlines the uphill battle faced by the White House drive for new gun regulations, after a school massacre that killed 26 in December. Polls show a majority of Americans back a ban on assault weapons.
The bill’s sponsor, Democratic Senator Dianne Feinstein, says such guns have been used in too many mass shootings. But opponents say the measure would violate the Second Amendment, the clause in the US Constitution that refers to the right of citizens “to keep and bear arms”.
Critics also argue it would hamper the ability of citizens to defend themselves from criminals with illegal guns. The same Senate committee has already approved expanding the requirement for background checks on gun buyers, increasing penalties for gun traffickers and boosting aid for school safety.
Thursday’s measure would ban the sale of 157 kinds of semi-automatic weapons, guns that automatically reload, and large-capacity ammunition magazines carrying more than 10 rounds.
But it allows 2,258 rifles and shotguns that are frequently used by hunters and does not include weapons already lawfully owned. Ms Feinstein said such exemptions would leave Americans with more than enough weapons to defend themselves. “Do they need a bazooka?” she asked at the hearing. “I don’t think so.”