“It’s time for the president to stand up and lead,” Mr. Bloomberg, an independent who endorsed Mr. Obama for re-election, said during an appearance on “Meet the Press” on NBC. “This should be his No. 1 agenda. He’s president of the United States. And if he does nothing during his second term, something like 48,000 Americans will be killed with illegal guns” in the next year.
Mr. Bloomberg noted that he had given his sought-after endorsement to the president because he agreed with his views on matters like gun control. But in blunt terms, the mayor said he now expected more from Mr. Obama.
“The president has to translate those views into action,” he said. “His job is not just to be well-meaning. His job is to perform and to protect the American public.”
Mr. Bloomberg was among an array of elected officials who appeared on the Sunday morning talk shows, to express sadness and shock over the killings at Sandy Hook Elementary School in Newtown — and discuss the need to strengthen to the nation’s gun laws.
Advocates for gun rights were noticeably absent among the television guests. David Gregory, the host of “Meet the Press,” noted that the show invited “31 pro-gun rights senators” to join in the discussion. “We had no takers,” he said.
In an interview on Sunday, Representative Peter T. King, Republican of New York, who is the chairman of the Homeland Security Committee, renewed his call for tougher gun restrictions, including banning assault weapons, requiring background checks for firearm purchases at gun shows and prohibiting gun sales to anyone on the nation’s terrorism watch list.
But Mr. King said he doubted that the shootings in Connecticut would alter the gun debate in Congress, saying that outside the Northeast a gun culture exists that is resistant to any kind of firearms regulation. “I hope I am wrong,” he said, “but I don’t think it will have a major impact on the debate in Congress. We’ve had a number of gun tragedies in recent years without any action being taken.”
A senior aide to a top Democrat in Congress echoed that sentiment, saying he was doubtful that there would be enough votes, even now, for passage of a ban on assault weapons.
Adam Lanza, the 20-year-old man who the police said killed 27 people in the rampage on Friday, had a small arsenal of firearms with him: Sig Sauer and Glock handguns and a Bushmaster rifle. The authorities said the firearms were registered to his mother, Nancy Lanza, whom he also killed. There was only one survivor among the victims.
During an appearance on the CNN program “State of the Union,” Gov. Dannel P. Malloy of Connecticut, a Democrat, asked why anyone would need to possess those kinds of firearms.
“You don’t hunt deer with these things,” he said. “And I think that’s the question that a lot of people are going to have to resolve their own minds: Where should this line get drawn?”
In a separate appearance on “Meet the Press,” Senator Dianne Feinstein, Democrat of California, said she would begin pushing her colleagues in Congress to pass an assault-weapons ban in the coming weeks.
“I’m going to introduce in the Senate, and the same bill will be introduced in the House — a bill to ban assault weapons,” Ms. Feinstein said.
Democrats have repeatedly failed in their efforts to pass an assault-weapons ban in Congress since a law prohibiting such weapons expired in 2004. In fact, Ms. Feinstein called for a renewal of the ban earlier this year after another deadly mass shooting, in a movie theater in Aurora, Colo.
Appearing on “Fox News Sunday,” Senator Joseph I. Lieberman, an independent from Connecticut who is retiring, also spoke in favor of renewing the federal ban on assault weapons.
He also said that the authorities needed to better understand what causes episodes of mass violence in order to prevent them from occurring. “I think we need a national commission on mass violence,” Mr. Lieberman said.
