Nine time world champion Valentino Rossi, the most experienced rider in the MotoGP paddock, fully backed the decision to hand Deniz Oncu a two-race ban for Sunday's shocking Moto3 accident in Austin.

But the Italian also made clear the problem of dangerous riding has been brewing for a while and compared the decision to send the junior class out for a frantic 5-lap restart to 'Russian roulette'.

Oncu triggered the Austin accident by 'swerving' in front of Jeremy Alcoba as he slipstreamed past the Italian on the back straight. Rossi's VR46 Academy rider Andrea Migno was the first to then strike Alcoba's fallen bike, followed by title leader Pedro Acosta.

Miraculously, all four escaped serious injury, but the huge accident came just a week after the third teenage fatality of the season in Moto3/SSP300 racing, at Jerez.

"I don’t want to say about Oncu or another rider, but for me the penalty is right. They have to do something. He has to stay at home for two races, minimum. They have to do something serious because the situation is completely out of control, for me," Rossi said.

"Oncu moved on the straight when he knew he had another rider on the side and caused a crash that potentially could be more than a crash. I was very, very scared for everybody, also because I have Migno there, and Acosta made a terrifying crash and they are very, very lucky that nothing happened.

"They have to do really something serious for these young guys from the beginning. They have to stay at home. They have to not race. I think that it's right because the situation has to change before something happens.

"Motorcycle races are too dangerous to have this behaviour on track. You need to respect your safety and the safety of your rivals and this is the most important thing. More than one position.

"Because here you can play with the life of a young guys and it's potentially a disaster."

But the Italian also felt race organiser's shared some of the blame for sending the Moto3 class out for such a short restart.

The original race had been stopped at the end of lap 7 of 17 after an accident for Filip Salac. Presumably due to time constraints, the minimum required race distance of 5 laps was then chosen for the restart.

"Today they make a mistake because they made Moto3 restart for 5 laps and it's too dangerous. For 5 laps it's like Russian roulette. When you put one bullet in the gun and [spin the cylinder]," Rossi said.

After the second stoppage, the race result was taken from the end of the first race.

The inaugural COTA Moto3 Grand Prix, in 2013, was decided by a 5-lap restart, although on that occasion the original race had already completed 10 laps.