Updated

President Barack Obama will deliver an opening message before the debut of "Speak Up," a Cartoon Network documentary about bullied youth across America and those who have helped them.

The half-hour film, part of the network's "Stop Bullying: Speak Up" initiative, will be aired on Sunday at 5:30 p.m. EDT/PDT, with an encore at 8 p.m.

The documentary features appearances by star athletes Venus Williams, Chris Webber, Lisa Leslie, soccer player Hope Solo, BMX bike rider Matt Wilhelm and NASCAR drivers Trevor Bayne, Jeff Burton and Joey Logano.

The film will also post on www.StopBullyingSpeakUp.com and be available through other outlets including Facebook, iTunes and YouTube after the premiere.

Obama, who has said he endured school-yard harassment, hosted the first anti-bullying summit at the White House last year.