In a press conference on Capitol Hill Thursday morning, Connecticut Sens. Richard Blumenthal LAW ’73 and Chris Murphy joined California Sen. Dianne Feinstein as she introduced legislation to ban assault weapons in the wake of December’s mass shooting in Newtown, Conn.

If passed, the legislation, titled the Assault Weapons Ban of 2013, will ban the sale, transfer, importation and manufacture of assault weapons while expanding the kinds of firearms categorized as assault weapons. The ban’s introduction comes just over one week after President Obama announced a series of executive actions and legislative initiatives, including an assault weapons ban, intended to curtail gun violence. But the proposed ban faces strong opposition from gun rights supporters and certain members of both houses of Congress.

“It will be a tough, demanding debate,” Blumenthal told the News Thursday. “But I’m hopeful. No single measure can be a solution. There’s no panacea, but these are reasonable regulations.”

The ban has already come up against fierce criticism from gun rights groups across the nation. The National Rifle Association, which counts over 4 million members, released a statement on Thursday stating that Feinstein “has been trying to ban guns from law-abiding citizens for decades.”

“The American people know gun bans do not work, and we are confident Congress will reject Sen. Feinstein’s approach,” the statement said.

Scott Wilson, president of the Connecticut Citizens Defense League, a gun-rights organization with approximately 3,000 members, said he thinks the bill is unlikely to pass, adding that “House [of Representatives] Republicans will put up a pretty good fight.”

Nevertheless, Feinstein, Blumenthal and Murphy said the importance of enacting gun control legislation outweighs staunch resistance both inside Washington and across the nation. Blumenthal said that despite the influence of the gun lobby, public opinion has shifted decisively in favor of gun control since the Newtown shooting, adding that “there has been a sea change in public consciousness, a seismic shift in public support.”

“If assault weapons and high capacity magazines were not so readily available, including the weapon Adam Lanza used to take 26 lives last month, there would be more little boys and girls alive in Newtown today,” Murphy said.

In addition to listing 157 specific firearms as assault weapons, the ban also defines any semi-automatic rifle, handgun or shotgun that can accept a detachable magazine and has at least one military characteristic as an assault weapon. Semi-automatic rifles and handguns with fixed magazines that accept more than 10 rounds fall under the proposed assault weapon definition as well. The new definition of assault weapons is significantly more expansive than previous iterations — the 1994 Assault Weapons Ban, which expired in 2004, defined assault weapons as those with detachable magazines and two or more military characteristics.

The proposed legislation also bans all ammunition feeding devices, such as magazines, clips and drums capable of holding more than ten rounds.

The 1994 ban, which gun advocates claim was ineffective in stemming the tide of gun violence, has come under criticism from supporters of tighter regulation for allowing firearm manufacturers to circumvent the definition of an assault weapon easily.

“The main lesson [of the 1994 ban] is that we should prevent an assault weapons ban that allows exceptions and exemptions,” Blumenthal said.

The fate of the legislation is likely to be decided by moderate senators, such as Tim Kaine and Mark Warner, both Democrats of Virginia. Many moderate legislators have yet to take a stance on the issuse formally. On Thursday, an aide to Sen. Kaine remained noncommittal on how the senator is likely to vote.

“He supports a comprehensive approach to reducing gun violence,” Lily Adams, a press secretary for Kaine, said in a Thursday email to the News. “Sen. Kaine also believes we should adopt reasonable restrictions on super-size magazines and combat weapons, and looks forward to reviewing bills aimed at curbing gun violence.”

Only hours after the announcement of the proposed legislation, Vice President Joe Biden, who led a task force that proposed federal actions to reduce gun violence, participated in a “hangout” on Google Plus on the topic of gun control. Tomorrow, Biden will travel to Richmond, Va., to campaign for the president’s proposals on gun control.

According to the United Nations Office on Drugs and Crime, the United States had 3.75 gun-induced homicides per 100,000 people in 2009, compared to 0.03 in the United Kingdom.

Correction: Jan. 28

A previous version of this article mistakenly stated that Senator Chris Murphy spoke to the News, when in fact he was quoted speaking on Capitol Hill.