The American underdogs in what is planned to be the world's first giant robot battle have enlisted help from NASA engineers and Hollywood robotics experts in a bid to overcome their favoured Japanese adversary.

MegaBots Inc., an Oakland, Calif.-based startup, has built a 4.5-metre-tall mechanical gladiator called the Mark II and challenged a Japanese firm to an international battle for supremacy.

But the Mark II isn't quite ready to take on Tokyo-based Suidobashi Heavy Industry's Kuratas robot, a more polished fighting machine with a big, agile hand that mimics the movements of its human pilot's hand.

"Our current robot, the Mark II, looks pretty intimidating," MegaBots co-founder Matt Oehrlein said. "The truth is, it's pretty slow. It's top-heavy. It's rusty, and it needs a set of armour upgrades to be able to compete in hand-to-hand combat."

That's why MegaBots launched an online Kickstarter campaign and raised more than $550,000 US from robot fans to turn the Mark II into a real fighting machine — faster, tougher, more balanced and equipped with detachable weapons such as a giant chain saw or punching fist.

The startup has enlisted the help of engineers from NASA, software maker Autodesk and the TV shows Mythbusters and BattleBots.

"We're absolutely confident that Team USA can beat Japan. We've assembled the best of the best of this country. We're not going to let our country down," company co-founder Gui Cavalcanti said.

UFC meets Formula 1

The original Mark II weighed 6.8 tonnes, had massive paintball guns in place of arms and required two pilots to operate. The Kuratas, which has been in development for three years, is much lighter than its American rival at 4.5 tonnes, has a single pilot and carries a BB Gatling cannon capable of firing 6,000 rounds per minute.

Suidobashi has been releasing impressive YouTube videos touting its machine's features for years.

The exact date and location of the battle between the human-piloted robots have yet to be determined, but it's expected to take place next June.

Win or lose, it's all part of MegaBots' plan by to make gladiator-style robot combat into big-time entertainment — a mix between the Ultimate Fighting Championship and Formula One auto racing — while developing new industrial technologies and inspiring a new generation of engineers.

There have already been several television shows featuring smaller, remote-controlled and typically wheeled robots fighting each other in front of audiences, but the MegaBots founders envision an entire sports league where teams from around the world build huge humanoid machines that throw each other down in stadiums filled with screaming fans.

"Everyone wins as long as there is robot carnage," said Oehrlein, an electrical engineer. "People want to see these things fight. They want to see them punch each other, they want to see them ripped apart and they want to be entertained."

'Fantastic spectator sport'

MegaBots was launched in 2014 by Oehrlein, Cavalcanti and Brinkley Warren, who grew up playing video games like MechWarrior and BattleTech and wanted to fulfil their dreams of watching massive machines fight.

"We want to bring the giant robots from science fiction and movies and video games to life because now we have the technology," said Cavalcanti, a robotics engineer. "It's really about: How do we put on the best show? How do we make the coolest fight?"

Robot enthusiasts like Gordon Kirkwood are eagerly anticipating the fight.

"I think it's going to be a smash hit," said Kirkwood, a robotics engineer in San Francisco. "This has the potential to be a fantastic spectator sport that people would really pay good money to see."