Washington (AP) — Spurred by a horrific elementary school shooting, President Barack Obama vowed to send Congress new policy proposals for reducing gun violence by January.

"This time, the words need to lead to action," Obama said Wednesday. He tasked Vice President Joe Biden with leading an administration-wide effort to create the new recommendations and pledged to push for their implementation without delay.

The president, who exerted little political capital on gun control despite a series of mass shootings in his first term, bristled at suggestions that he had been silent on the issue during his first four years in office. But he acknowledged that Friday's deadly shooting had been "a wake-up call for all of us."

Twenty children and six adults were killed when a man carrying a military-style rifle stormed Sandy Hook Elementary in Newtown, Conn., Friday morning.

The president also called on Congress Wednesday to reinstate an assault weapons ban that expired in 2004 and to pass legislation that would close the gun show "loophole," which allows people to purchase firearms from private dealers without a background check. Obama also said he wanted Congress to pursue the possibility of limiting high-capacity ammunition clips.

"The fact that this problem is complex can no longer be an excuse for doing nothing," Obama said. "The fact that we can't prevent every act of violence doesn't mean we can't steadily reduce the violence."

The president's announcement Wednesday underscores the urgency the White House sees in formulating a response to the Newtown shooting. The massacre has prompted several congressional gun rights supporters to consider new legislation to control firearms, and there is some concern that their willingness to engage could fade as the shock and sorrow over the Newtown shooting eases.

Obama said it was "encouraging" to see people of different backgrounds and political affiliations coming to an understanding that the country has an obligation to prevent such violence.

Appealing to gun owners, Obama said he believes in the Second Amendment and the country's strong tradition of gun ownership. And he said "the vast majority of gun owners in America are responsible."

"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," Obama said.

Obama also tasked the Biden-led team with considering ways to improve mental health resources and address ways to create a culture that doesn't promote violence. The departments of Justice, Education, Health and Human Services, and Homeland Security, along with outside groups and lawmakers, will all be part of the process.

Biden's prominent role in the process could be an asset for the White House in getting gun legislation through Congress. The vice president spent decades in the Senate and has been called on by Obama before to use his long-standing relationships with lawmakers to build support for White House measures.

The president challenged the National Rifle Association, the country's most powerful gun lobby and key backer of many Republican politicians, to join the broader effort to reduce gun violence as well.

"Hopefully they'll do some self-reflection," Obama said of the NRA.

The NRA made its first comments since the shooting on Tuesday, promising to offer "meaningful contributions to help make sure this never happens again."

Obama said that while taking the necessary steps to reduce gun violence would take commitment and compromise, he said it could be achieved if Washington summons "even one tiny iota of the courage of those teachers, that principal in Newtown summoned on Friday."