New York Mayor Michael Bloomberg is leading a push for tougher gun laws in the wake of Friday's mass killing at a Connecticut elementary school.

Flanked by dozens of shooting survivors and relatives of victims of gunfire around the country, Bloomberg pressed Congress and President Barack Obama to take action, asking if a massacre, which left 20 children aged 6 and 7 and their teachers dead, doesn't prompt action, what will?

At the White House, spokesman Jay Carney said curbing gun violence is a complex problem that will require a comprehensive solution.

Sen. Mark Warner, a Virginia Democrat, says the attack in Newtown has led him to rethink his opposition to the ban on assault weapons.

West Virginia Sen. Joe Manchin, a Democrat who is an avid hunter and lifelong member of the National Rifle Association, said it's time to move beyond the political rhetoric and begin an honest discussion about reasonable restrictions on guns.