WASHINGTON -- A U.S. senator and lifelong member of the National Rifle Association became the most prominent gun rights advocate to speak out after last week's school shooting, saying Monday it was time for the debate to move beyond political rhetoric and begin an honest discussion about reasonable restrictions on guns.

But White House spokesman Jay Carney cautioned, "No single piece of legislation or action will fully address the problem."

It remained unclear how President Barack Obama would move forward on his comments to use the "power" of his office to tackle gun violence.

As many gun-rights advocates and politicians remained silent, the killing of 20 children as young as 6 years old led conservative Democratic Sen. Joe Manchin to speak out Monday.

"Never before have we seen our babies slaughtered. It's never happened in America that I can recall, seeing this carnage," Manchin told MSNBC. "Anybody that's a proud gun owner, a proud member of the NRA, they're also proud parents, they're proud grandparents. They understand this has changed where we go from here."

The self-described "proud outdoorsman and hunter" added, "I don't know anyone in the sporting or hunting arena that goes out with an assault rifle, I don't know anybody who needs 30 rounds in a clip to go hunting."

Manchin said he agrees with New York City Mayor Michael Bloomberg, who has advocated banning the sale of assault weapons.

Democrats say the "meaningful action" Obama has spoken of in the wake of last week's shooting must include a ban on the military-style assault weapons and a look at how the country deals with individuals suffering from serious mental illness.

On Sunday, several Democratic lawmakers, and Independent Sen. Joe Lieberman from Connecticut, said it was time to take a deeper look into the recent series of mass shootings and what can be done.

Gun control was a hot topic in the early 1990s, when Congress enacted a 10-year ban on assault weapons. But since that ban expired in 2004, few Americans have wanted stricter laws, and politicians say they don't want to become targets of a powerful gun rights lobby.

Gun rights advocates said that might all change after the latest shooting, which killed 20 children aged 6 or 7, along with six adults.

"I think we could be at a tipping point ... a tipping point where we might actually get something done," said Sen. Chuck Schumer on CBS' "Face the Nation."

Speaking Sunday night at a vigil in Newtown, Connecticut, the site of Friday's massacre, Obama did not specifically address gun control. But he vowed, "In the coming weeks I'll use whatever power this office holds to engage my fellow citizens, from law enforcement to mental health professionals to parents and educators in an effort aimed at preventing more tragedies like this."

He added: "Are we really prepared to say that we're powerless in the face of such carnage, that the politics are too hard? Are we prepared to say that such violence visited on our children year after year after year is somehow the price of our freedom?"

Lieberman said a new commission should be created to look at gun laws and the mental health system, as well as violence in movies and video games.

"Assault weapons were developed for the U.S. military, not commercial gun manufacturers," said Lieberman, who is retiring next year.

Sen. Dianne Feinstein said she will introduce legislation next year to ban new assault weapons, as well as big clips, drums and strips of more than 10 bullets. Congress is expected to adjourn soon for the upcoming Christmas holiday.

"It can be done," Feinstein told NBC's "Meet the Press" of reinstating the ban despite deep opposition by the National Rifle Association and similar groups.

Bloomberg said Obama could use executive powers to enforce existing gun laws, as well as throw his weight behind legislation like Feinstein's.

"It's time for the president, I think, to stand up and lead and tell this country what we should do -- not go to Congress and say, 'What do you guys want to do?"' Bloomberg told NBC's "Meet the Press."

On Monday, Bloomberg joined with dozens of shooting survivors and victims' relatives to call on tougher gun laws. He said the shooting "demands immediate national action."

Gun rights activists have remained largely quiet on the issue since Friday's shooting.

David Gregory, the host of "Meet the Press," said NBC invited all 31 "pro-gun" senators to appear on Sunday's show, and all 31 declined.

Republican Rep. Louie Gohmert of Texas was the sole representative of gun rights' activists on the various Sunday political talk shows. In an interview on "Fox News Sunday," Gohmert defended the sale of assault weapons and said that the principal at Sandy Hook Elementary School, who authorities say died trying to overtake the shooter, should herself have been armed.

"I wish to God she had had an M-4 in her office, locked up so when she heard gunfire, she pulls it out and she didn't have to lunge heroically with nothing in her hands. But she takes him (the shooter) out, takes his head off before he can kill those precious kids," Gohmert said.

Gohmert also argued that violence is lower in cities with lax gun laws, and higher in cities with stricter laws.

"The facts are that every time guns have been allowed -- conceal-carry (gun laws) have been allowed -- the crime rate has gone down," Gohmert said.

Gun control advocates say that isn't true. A study by the California-based Law Center to Prevent Gun Violence determined that seven of the 10 states with the strongest gun laws -- including Connecticut, Massachusetts and California -- are also among the 10 states with the lowest gun death rates.