WASHINGTON - President Barack Obama on Wednesday announced a sweeping $500 million program to curb gun violence, setting up a fight over universal background checks and bans on military-style assault weapons and high-capacity ammunition magazines, in the wake of the Connecticut school shooting.

   Obama also used his presidential powers to issue 23 orders that don't require congressional approval. The largely incremental executive steps include requiring federal agencies to make more data available for background checks, appointing a fulltime director of the Bureau of Alcohol, Tobacco, Firearms and Explosives, and directing the Centers for Disease Control to research gun violence.

   But the president, speaking at the White House, acknowledged the most effective actions must be taken by lawmakers.

   "To make a real and lasting difference, Congress must act," Obama said. "And Congress must act soon."

   Obama was flanked by children who wrote him letters about gun violence in the weeks following the Newtown shooting. Families of the 20 children killed in the massacre, as well as survivors, were also in the audience along with law enforcement officers and members of Congress.

   "This is our first task as a society, keeping our children safe," Obama said. "This is how we will be judged."

   The president based his proposals on recommendations from an administration-wide task force led by Vice President Joe Biden.