President Barack Obama is announcing a $500 million package of executive actions and legislative proposals aimed at reducing gun violence a month after a mass shooting in Connecticut killed 20 elementary school children.

The package includes a call on Congress to ban military-style assault weapons and high-capacity magazine and it would close loopholes in the gun sale background check system.

President Obama also is signing 23 executive actions, which require no congressional approval , including several aimed at improving access to data for background checks. A presidential memorandum will instruct the Centers for Disease Control to research causes and prevention of gun violence.

In addition, President Obama will nominate Todd Jones as director of the Bureau of Alcohol, Tobacco, Firearms and Explosives. Jones currently is the acting director of the agency.

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

President 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," President 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.