Obama calls for tougher background check on would-be gun-owners

US President Barack Obama has called for tougher background checks on Americans trying to buy a gun as he and Republican challenger Mitt Romney engaged in their most extensive discussions on the gun control issue since last week’s massacre in a Colorado theatre.

Their pointed comments revived a debate – if briefly – that has faded to the background in national politics and been virtually non-existent in this year’s close presidential race.