WASHINGTON - President Barack Obama vowed to press for tighter gun laws early next year, as he sought to turn national outrage over the Connecticut school massacre into action to ban assault weapons and ensure better background checks on gun buyers.

Obama held a White House news conference on Wednesday to announce that Vice President Joe Biden will lead an interagency effort to craft new gun policies. The group is expected to offer its proposals in January.

"We know this is a complex issue that stirs deeply held passions and political divides," Obama said. "But the fact that this problem is complex can no longer be an excuse for doing nothing."

Biden and other cabinet members planned to meet with law enforcement leaders from across the country to discuss policy ideas on Thursday, a White House official said.

Obama said he believed most Americans support the reinstatement of a ban on the sale of military-style assault weapons, barring the sale of high-capacity ammunition clips and a law requiring background checks on buyers before all gun purchases, to stop sales at gun shows without such checks.

Saying gun control cannot be the only solution to the problem, Obama also expressed support for making it easier for Americans to get access to mental health care - "at least as easy as access to a gun."

Obama urged Congress to quickly pass new measures next year.

The killing of 20 young children and six adults at a elementary school in Newtown, Connecticut, last Friday has even shifted pro-gun advocates away from long-held views in a way that previous mass shootings have not.

Friday's massacre by a 20-year-old man was the fourth shooting rampage to claim multiple lives in the United States this year.

Under pressure from fellow Democrats, Obama insisted the guns issue would not be ignored this time.

But changing the rules will be difficult.

Most Republicans remain staunchly opposed to tighter gun laws, particularly in the House of Representatives, where the party holds a majority. Robert Goodlatte, a Virginia congressman who will be chairman of the House Judiciary committee next year, said flatly in Roll Call this week he opposed gun control.

With Biden at his side, Obama said the group would give him proposals he could outline in his State of the Union speech in late January. Cabinet members involved include Attorney General Eric Holder, Homeland Security Secretary Janet Napolitano, Health and Human Services Secretary Kathleen Sebelius and Education Secretary Arne Duncan.

"This is not some Washington commission. This is not something where folks are going to be studying the issue for six months and publishing a report that gets read and then pushed aside. This is a team that has a very specific task to pull together real reforms right now," Obama said.

Obama has tapped Biden to lead other high-profile initiatives, including efforts on a deficit-reduction compromise with congressional Republicans in 2011.