WASHINGTON — Vice President Joe Biden tried to drum up support for the Obama administration’s gun control proposals Wednesday, arguing that the Newtown massacre in December fundamentally changed the public mood.

“The excuse that it’s too politically risky to act is no longer acceptable,” Biden said in a meeting of the National Association of Attorneys General. “We cannot remain silent.”

Biden advocated a series of proposals, including universal background checks for gun buyers, a ban on military-style weapons, a limit on the size of ammo magazines and a gun trafficking statute. The vice president, who helped author  a 1994 assault weapons ban that expired in 2004, said none of the proposed measures infringe on Second Amendment rights.

His remarks come as the Senate Judiciary Committee neared a vote on a new assault weapons ban and other gun control legislation, the first roll calls on Capitol Hill since the Newtown shooting that killed 26 students and staff at an elementary school in Connecticut.

Noting that 75 days have passed since the Newtown tragedy, Biden said Americans are entitled to see their elected representatives vote on gun control proposals — even though legislation may not prevent all mass shootings.

“We know we can’t save every life,” Biden said.

But the administration’s proposals are certain to face opposition on Capitol Hill from the National Rifle Association and many Republican members of Congress, who do not support significant changes to gun legislation.

Sen. Patrick Leahy, D-Vt., the Judiciary Committee chairman, said his panel will consider a universal background checks bill, a school safety bill, a gun trafficking statute and an assault weapons ban. By breaking Obama’s gun control agenda into individual items, Senate Democrats hope that some of the least controversial measures — such as expanded background checks — can be passed into law.

In the Senate, a universal background checks bill has been stalled for two weeks over maintenance of records for private gun sales. If no records were kept, Biden said, the legislation would be severely diluted. The bill would close loopholes to require background checks at gun shows and in other private sales.

“The proposals they’re arguing as they mark up the legislation in the United States Senate are so porous that they are going to allow a truck to be driven through the holes in the legislation they are proposing, loaded with tens of thousands of weapons,” he said.

Biden acknowledged the tough legislative fight ahead, saying that the voices of many stakeholders will join the gun control debate. But he said the beliefs and tactics of some gun rights groups like the NRA no longer align with public opinion.

“The organized opposition is hoping the urgency diminishes,” he said. “Connecticut is not going to fade from the memory of the American people.”

More than half of Americans — 52 percent — say the Newtown shooting has made them more supportive of gun control, according to a January Washington Post-ABC News poll.

The vice president cited the victory of former Illinois state legislator Robin Kelly, a vocal proponent of gun control, in a Democratic primary Tuesday night as evidence of the public’s push for gun law reform. Kelly, who will replace the disgraced Jesse Jackson Jr. in Congress, campaigned for tougher gun legislation in a contest against Debbie Halvorson, a former congresswoman rated highly by the NRA.

Her success at the polls, Biden said, emphasizes that politicians will suffer politically if they do not act on gun control.

“The voters sent a message last night, not just to the NRA but to politicians all around the country by electing Robin Kelly,” Biden said. “The message is there will be a moral price as well as a political price to pay for inaction.”