President Barack Obama is asking a team led by Vice President Joe Biden to offer "concrete proposals" to curb gun violence no later than January, in the aftermath of the massacre at a Connecticut elementary school.

Obama said after he receives recommendations from Biden's group, he will push legislation "without delay." The president is urging Congress to hold votes on the bill.

Obama said the issue is complex but "we have a deep obligation -- all of us -- to try."

Biden, a longtime gun-control advocate, will lead a team that will include members of Obama's administration and outside groups.

The move comes after Friday's shooting at Sandy Hook Elementary in Newtown, Conn. Twenty children and six adults were killed at the school by a gunman wielding a semi-automatic rifle.

The president also called on Congress Wednesday to reinstate an assault-weapon 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.

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."

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