Following the slaughter of 27 on Friday in Connecticut, Sen. Dianne Feinstein of California said she will introduce a bill to reinstate the assault weapons ban, which expired in 2004. NBC's Peter Alexander reports.

Friday's school shooting in Connecticut prompted a renewed effort by lawmakers to re-evaluate gun rights, as a top Democrat vowed Sunday to introduce new legislation on the first day of the new Congress next year.

The massacre at an elementary school in Newtown, Conn. left 28 dead, including 20 students, seven adults and the suspected shooter, leading proponents of gun control to redouble their efforts to seek new regulations. New York City Mayor Michael Bloomberg, an outspoken advocate of gun control, said the issue should now be atop President Barack Obama's second term agenda.

To that end, California Sen. Dianne Feinstein, D, said she intended to introduce a gun control bill on the first day of the next Congress. Paired with a twin version in the House, Feinstein's law would take aim at limiting the sale, transfer and possession of assault weapons, along with the capacity of high-capacity magazines.

"It can be done," she said on NBC's "Meet the Press." The senator, a proponent of gun control, said she expected Obama to offer his public support for the law.

Sen. Dianne Feinstein says on Meet the Press that she'll introduce a measure to reform gun ownership standards in the next Congress.

A federal ban on assault weapons, first passed in 1994 and signed by President Bill Clinton, expired in 2004. And while Obama has said he favors its reinstatement, the administration has hardly thrown its weight behind such a proposal during his first term.

The especially grisly shooting in Connecticut — which follows several other high-profile shootings at a movie theater in Aurora, Colo., and outside a Sikh temple in Wisconsin — might now serve as a catalyzing moment in that dormant gun debate.

"We're going to have to come together and take meaningful action to prevent more tragedies like this, regardless of the politics," Obama himself said on Friday in the aftermath of the Newtown shooting.

Outspoken proponents of gun control, like Bloomberg, have now begun to pressure the president to speak out more forcefully on the issue.

"It's time for the president to stand up and lead and tell this country what we should do," said the New York City mayor. "This should be his No. 1 agenda."

There are indications that some of the most commonly discussed measures to rein in weapons enjoy some degree of public support. An early August CNN/ORC poll, conducted in the aftermath of the Colorado and Wisconsin shootings, found varying levels of public support for different gun control proposals. Fifty-seven percent of adults, for instance, said they favored a ban on the manufacture, sale and possession of assault weapons, and 60 percent said they supported a ban on the possession of high-capacity ammunition clips.

But gun owners' groups, like the National Rifle Association, could prove a significant political obstacle to moving any such proposals through Congress. The NRA — which endorsed Obama's Republican opponent, Mitt Romney, during the presidential campaign — remains a formidable political force. The group could target, for instance, Democrats from rural or centrist districts and states for defeat if they were to vote for such a law.

Bloomberg argued otherwise. "There is this myth that the NRA is so powerful," he said. "Today the NRA's power is so vastly overrated."

In the meantime, the mayor said, Obama could take action through executive orders to strengthen and update the background check system and more aggressively enforce existing laws.

On Sunday, the president will travel to Newtown to comfort victims' families and thank first responders for their efforts. Obama will also speak at a vigil this evening.