On Monday several members of Congress have said they are open to restrictions on assault weapons, and New York City Mayor Michael Bloomberg insisted it's time to take action. NBC's Tom Costello reports.

Updated 4:36 p.m. - A handful of pro-gun Democrats showed signs of willingness to consider strengthening regulations on firearms in the aftermath of last week’s elementary school shooting in Newtown, Conn.

But that might not mean anything without the cooperation of Republicans, whose senior leaders and rank-and-file members have been mute about their interest in cooperating in a legislative effort to curb gun violence, making the prospects for any new, federal gun law unclear.

After President Barack Obama vowed at a vigil Sunday evening in Newtown to lead “an effort aimed at preventing more tragedies like this,” several Democrats with long track records of supporting gun rights said they would be willing to consider new proposals, like renewing the ban on assault weapons or limiting the capacity of ammunition magazines that are available for sale.

"Anyone saying they don't want to talk and sit down and have that type of dialogue is wrong," West Virginia Sen. Joe Manchin, D, said Monday morning on MSNBC. "Everything should be on the table."

If gun laws are going to be changed, advocates will have to overcome past opposition from strong NRA supporters in Congress. Sen. Joe Manchin, a lifelong member of the National Rifle Association, D-W.V., discusses.

That pronouncement carries a degree of weight, considering the source. Manchin has won endorsements and support from the National Rifle Association during his career, and even appeared in a 2010 campaign ad shooting a copy of the cap-and-trade environmental regulatory bill.

Another West Virginia Democrat, Rep. Nick Rahall, also suggested he was interested in action.

"As a lifelong defender of the Second Amendment, I believe that gun safety is essential, but, so is addressing the gaps in our mental health system and the issue of drugs and violence in our culture and prayer in our schools," he said in a statement. "Let us act deliberately, but, for the sake of too many already lost, let us act."

A Kentucky Democrat, Rep. John Yarmouth, a prior proponent of an assault weapons ban who hails from a Republican-leaning state, went so far as to apologize to the 27 victims of the Newtown shooting on Monday for not having pushed harder for new laws.

“I have been largely silent on the issue of gun violence over the past six years, and I am now as sorry for that as I am for what happened to the families who lost so much in this most recent, but sadly not isolated, tragedy,” he said in a statement.

NBC News' Chuck Todd joins a conversation on the Newtown shooting and what the political response may be. Will the president tackle gun reform in a second term? Todd thinks it could be possible.

And Virginia Sen. Mark Warner, a Democrat who has had an “A” rating from the NRA, called the Connecticut shooting a “game changer” in terms of gun control.

“I join with the president – and, I think reasonable people in both parties and the overwhelming majority of Americans who are gun owners who believe that we’ve got to put stricter rules on the books,” he told a CBS affiliate in Richmond.

One of the reasons major gun legislation hasn’t advanced through Congress in recent years is the increased number of gun-friendly Democrats elected from swing districts and more culturally conservative states. The influx of these pro-gun Democrats made new gun control regulations a virtual impossibility.

But no Republican leader – so far – has joined this Democratic chorus in calling for stricter control of guns in the aftermath of the Newtown massacre. And a new poll, conducted in the aftermath of the Connecticut incident and released on Monday, showed that opinion on gun laws had only shifted marginally in the days following this most recent mass shooting.

Fifty-four percent of Americans said in a Washington Post/ABC News poll released Monday that they favor stricter gun control laws – a slight uptick in the poll numbers preceding Newtown, but hardly near the 67 percent who favored tighter gun control in May 1999, following the massacre at Columbine High School in Colorado. And more Americans – 49 percent – said the most effective way to curb gun violence is through enforcing existing laws, versus 32 percent who favor passing new laws.

That said, 52 percent of Americans now believe that the recent shootings are emblematic of larger problems in society, a sea change from July 2012, when 67 percent of Americans, in the aftermath of the movie theater shooting in Aurora, Colo., said recent mass shootings were more likely the isolated acts of troubled individuals.

In the meanwhile, Democrats are girding for a potential fight in Congress next year over guns after California Sen. Dianne Feinstein, D, said will introduce new legislation on the first day of the next Congress to reinstate the assault weapons ban, which lapsed in 2004. Other Democrats have discussed including rules to limit the capacity of ammunition magazines, or to address mental health.

One pro-gun Democrat who faces re-election in 2014, Alaska Sen. Mark Begich, emphasized mental health in a statement Monday and sidestepped any mention of guns.

"After multiple tragedies across the country, there is no doubt that we must do more to keep our families and communities safe and that is why I believe we must start with the ever-pressing issue of mental health services in this country," he said.

Feinstein said Monday on MSNBC that she had called the president this morning to enlist his support for her bill, but hadn’t heard back.

"I'd like to talk to him about his help in moving forward with this,” she said.