WASHINGTON » In the emotional statement on the Newtown, Conn., shootings that President Barack Obama delivered from the White House on Friday, it was a single line, spoken as much in anger as in grief, that stood out. The words were cautious and were immediately criticized for being too timid. But they may have signaled that the long-dormant debate over the nation’s gun laws is about to be re-engaged.

"We’re going to have to come together and take meaningful action to prevent more tragedies like this, regardless of the politics," Obama said, listing the devastation wrought by other gun violence, from a recent attack at an Oregon shopping mall to the shootings in a movie theater in Aurora, Colo., in July.

But New York Mayor Michael R. Bloomberg spoke for many gun-control advocates, who have been frustrated and disappointed by Obama’s failure to embrace the issue, when he said he wanted to hear much more.

"Calling for ‘meaningful action’ is not enough. We need immediate action," said Bloomberg, who is leader of a group of mayors against illegal gun ownership.

White House officials professed not to know what Obama’s pledge for "meaningful action" meant. And the president stopped short of detailing any new initiatives.

Pressed about whether Obama would use the tragedy to fuel a new effort, White House spokes­man Jay Carney said the administration did not want to politicize a tragedy.

But politics intruded almost immediately. Bloomberg’s group organized a vigil in front of the White House to demand action. On Capitol Hill there was an outpouring of condolences and a predictably partisan split on how to respond.

Republicans and many moderate Demo­crats expressed their horror at the mass killing but were either silent on a legislative response or said it was not time to talk about gun control. But liberal Demo­crats said it was time to move forward with serious gun laws.

Rep. Carolyn McCarthy, D-N.Y., whose husband was one of six people killed in a shooting on the Long Island Rail Road in 1993, said she would resume her quest for broad gun-violence legislation, including reinstating the assault weapons ban that expired in 2004.

As the debate over gun control flares anew, it is likely to focus on the types of two of the guns that were found with Connecticut shooting suspect Adam Lanza: a Glock pistol and a Bushmaster .223 M4 carbine rifle, which are similar in type to the weapons used in the mass shootings in Oregon and Colo­rado. Both guns are popular for target shooting and self-defense, and have been singled out by gun-control advocates because of their ability to rapidly fire multiple rounds and accommodate large magazines.

But Republicans said tighter gun-control measures would be the wrong step.

"That’s one thing I hope doesn’t happen," said Rep. Mike Rogers, a senior Michigan Republican who is a former FBI agent. "What the more realistic discussion is, How do we target people with mental illness who use firearms?"

Kristen Rand, legislative director for the Violence Policy Center, a gun-control advocacy group, said it was too early to say whether the Newtown massacre would yield different political results from previous mass shootings, including the attack that nearly took the life of a member of Congress, Gabri­elle Giffords of Arizona.

But she said she believes it would for two reasons: The victims were children, which has elicited a gut-wrenching response across the country, and the National Rifle Association proved to be a political paper tiger in the 2012 election.

David Chipman, a former special agent at the Bureau of Alcohol, Tobacco and Firearms who is now a consultant to Mayors Against Illegal Guns, said he believed the shooting was "a game changer."

In Colorado, a state that was rocked by the 1999 Columbine High School massacre and the Aurora movie theater shooting, Friday’s massacre renewed debate over why mass shootings keep occurring and whether gun control can stop them.

"Until we get our acts together and stop making these … weapons available, this is going to keep happening," said an angry Tom Teves, whose son Alex was killed in the theater shooting.

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The Associated Press contributed to this report.