Oprah Winfrey has pledged to match actor George Clooney and his wife Amal in donating $US500,000 ($A700,000) to students organising protests against gun violence in the US.
Winfrey wrote on Twitter that she "couldn't agree more" with the actor, who had said "our children's lives depend on it", and said she would donate the same amount to the March For Our Lives fund.
"These inspiring young people remind me of the Freedom Riders of the 60s who also said we've had ENOUGH and our voices will be heard."
Clooney said he would attend next month's protest with his wife, a human rights lawyer, as he praised the "courage and eloquence" of the survivors of the Florida school shooting that killed 17.
Students turned into activists in the wake of the Stoneman Douglas High School atrocity and led calls for stricter gun controls in the country where school shootings have become routine.
The March For Our Lives protest, led by students, will see demonstrators gather in Washington DC to call for new laws to prevent the "rampant" gun violence.
"Every kid in this country now goes to school wondering if this day might be their last. We live in fear," its mission statement added.
The alleged gunman, 19-year-old former student Nikolas Cruz, is reported to have been legally sold the assault rifle used in the February 14 attack, despite having a history of mental health issues.
Survivors, stars and politicians called on the Republican Party and President Donald Trump to impose stricter gun controls in the wake of the attack, which was the eighth school shooting to cause injury or death this year.
Students from several Florida high schools also staged a walk-out on Tuesday in a showing of solidarity to the 14 students and three staff members killed.
Australian Associated Press