A major Republican donor vowed he would not write another campaign cheque unless candidates pledged to support a ban on assault rifles.

Al Hoffman Jr., a prominent Florida real-estate developer, said: "For how many years now have we been doing this — having these experiences of terrorism, mass killings — and how many years has it been that nothing's been done?"

"I will not write another check unless they all support a ban on assault weapons."

Hoffman's comments come after 19-year-old Nikolas Cruz killed 17 people at the Marjory Stoneman Douglas High School in Parkland, Florida, last week, renewing America's tortuous debate on gun control.

The teenage killer used a legally purchased AR-15, one of the most popular semi-automatic rifles in the US.

This rifle has featured in a number of mass shootings in recent years such as Las Vegas, Nevada; Sutherland Springs, Texas; Orlando, Florida; and Newtown, Connecticut.

Semi-automatic firearms, commonly referred to as "assault weapons," were previously banned under a 1994 law, but that lapsed in 2004.

Some students who survived the attack at the Parkland high school said they hold accountable politicians who accept money from America's influential gun lobby, the National Rifle Association (NRA).

Students from the high school are organising a protest called March for Our Lives, scheduled to take place on 24 March in Washington, and have invited other students across the country to take part.

Cameron Kasky, who survived the shooting, told CNN: "My message for people in office is you're either with us or against us. We are losing our lives while the adults are playing around.

"This isn't about the GOP [Republicans], this isn't about the Democrats, this is about us creating a badge of shame for any politicians accepting money from the NRA and using us as collateral."