WASHINGTON (AP) — Vice President Joe Biden said the nation could not wait any longer to respond to gun violence, telling mayors on Thursday that the White House would "take this fight to the halls of Congress."

Biden outlined President Barack Obama's sweeping proposal, announced Wednesday, during a speech to the United States Conference of Mayors, providing a rationale for a plan that includes a ban on assault weapons, the limiting of high-capacity ammunition magazines and requiring background checks for all gun buyers.

Obama's proposal, which is the broadest attempt to tighten gun laws in nearly two decades, faces an uncertain future in Congress, where lawmakers have resisted tougher laws in recent years and some members of Congress have responded warily to the president's plan. But Biden made clear that the White House would push aggressively for the plan following the deadly school shooting in Newtown, Conn.