WASHINGTON - Declaring the time for action overdue, President Obama promised on Wednesday to send Congress broad proposals in January for tightening gun laws and curbing violence after last week's schoolhouse massacre in Connecticut.

Even before those proposals are drafted, Obama pressed lawmakers to reinstate a ban on military-style assault weapons, close loopholes that allow gun buyers to skirt background checks, and restrict high-capacity ammunition clips.

"The fact that this problem is complex can no longer be an excuse for doing nothing," Obama said in his most detailed comments since Friday's killing of 20 schoolchildren and six adults in Newtown, Conn.

Gun-control measures have faced fierce resistance in Congress for years, but that may be changing because of last week's violence. Obama has signaled for the first time in his presidency that he is willing to spend political capital on the issue, and some gun-rights advocates on Capitol Hill - Democrats and Republicans - have expressed willingness to consider new measures.

Still, given the long history of opposition to tighter gun laws, there is no certainty the legislation Obama backed Wednesday or the proposals he will send to Congress next month will become law.

Obama tasked Vice President Biden with overseeing the process to create those proposals. Among those named to Biden's group was Philadelphia Police Commissioner Charles H. Ramsey.

Beyond firearms restrictions, officials will also look for ways to increase mental-health resources and consider steps to keep society from glamorizing guns and violence.

Obama's January deadline underscores the desire among White House officials to respond swiftly.

"I would hope that our memories aren't so short that what we saw in Newtown isn't lingering with us, that we don't remain passionate about it only a month later," Obama said. He pledged to talk about gun violence in his State of the Union address.

Obama has called for a national dialogue on gun violence before, but his words have not been backed up with concrete action. And some of the gun measures Obama has signed lessened restrictions on guns, allowing people to carry concealed weapons in national parks and in checked bags on Amtrak trains.

Obama bristled at suggestions that he had been silent on gun issues. But he acknowledged the Newtown shooting had been "a wake-up call for all of us."

The shooting appears to have had a similar impact on some on Capitol Hill. West Virginia Sen. Joe Manchin, a conservative Democrat and avid hunter, has said "everything should be on the table," as has 10-term House Republican Jack Kingston of Georgia.

Incoming House Judiciary Committee Chairman Robert Goodlatte (R., Va.) pledged to "listen to and carefully review suggestions made by the president's task force and other groups to see what we can do to prevent a terrible tragedy like this in the future."

New York City Mayor Michael Bloomberg, an independent who has been sharply critical of the president's lack of action on gun issues, called the effort a step in the right direction.

Obama reiterated his support for the Second Amendment. And he said no effort to reduce gun violence would be successful without their participation.

"I am also betting that the majority, the vast majority, of responsible, law-abiding gun owners would be some of the first to say that we should be able to keep an irresponsible, law-breaking few from buying a weapon of war," he said.

He also challenged the National Rifle Association to do "some self-reflection."

The NRA, in its first statements since the shooting, pledged Tuesday to offer "meaningful contributions to help make sure this never happens again."