WASHINGTON – Conceding “this will be difficult,” President Barack Obama urged a reluctant Congress on Wednesday to require background checks for all gun sales and ban both military-style assault weapons and high-capacity ammunition magazines in an emotion-laden plea to curb gun violence in America.

The president’s sweeping, $500 million plan, coming one month after the school massacre in Connecticut, marks the most comprehensive effort to tighten gun laws in nearly two decades. But his proposals, most of which are opposed by the National Rifle Association, face a doubtful future in a divided Congress where Republicans control the House.

Seeking to circumvent at least some opposition, Obama signed 23 executive actions Wednesday, including orders to make more federal data available for background checks and end a freeze on government research on gun violence. But he acknowledged that the steps he took on his own would have less impact than the broad measures requiring approval from Capitol Hill.