Mining billionaire Andrew Forrest has warned the Western Force could join a breakaway international competition as thousands of fans rallied against a decision to axe the club from Super Rugby.

The Force were dropped from the competition earlier this month following arbitration with the Australian Rugby Union (ARU), with the decision sparking anger among the club and its fans.

The ARU had argued financial reasons were behind the decision, but the Force have already taken legal action to save the club from being cut.

About 8,000 supporters gathered at Rugby WA headquarters in the Perth suburb of Floreat to voice their opposition to the ARU's decision.

Force captain Matt Hodgson and Mr Forrest — who threw his support behind the club during the campaign to save it — were among those who addressed the crowd.

The mining billionaire gave a passionate speech, saying the club would survive with or without the ARU.

"The ARU want to run a process that is not based on merit," he told the crowd.

Andrew Forrest accused the ARU of conducting a charade before dumping the Force. ( ABC News: Garrett Mundy )

"[If] they want to run a process that is based on the lucky drawcard of where you happen to live, or where you happen to support your sport, then we will start our own international league from here."

Not the end of the Force, Forrest says

When pressed on the comments, Mr Forrest reiterated his stance that the club would continue.

Supporters brought banners reading 'ARU: Anti Rugby Union' and 'No Force, No Future'. ( ABC News: Garrett Mundy )

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"This is absolutely not the end of the Western Force and not the end of rugby in Western Australia," he said.

"If anything, the hottest fires forge the strongest metals.

"This will make rugby in Western Australia stronger and stronger again."

The Western Australian of the Year did not hold back in his criticism of the ARU board, accusing it of secrecy.

"There's a group of people who wanted to conduct a charade which would harm thousands of people," he said.

"What we're seeing here is rugby [suffer] across Australia purely for a weak financial decision.

"If [the ARU board] is not good at finance, then hand over to people who are."

Force supporters young and old turned out to the rally. ( ABC News: Garrett Mundy )

We'll go down fighting: Hodgson

Earlier, Hodgson thanked the fans for their support in the wake of the ARU's decision.

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"It means a lot not only to me, but to the players and the staff who have gone through hell," he said.

"But we couldn't have done it without people like you being beside us, behind us and in front of us, leading the way for not only rugby at the Western Force but rugby in WA.

"It's bigger than the Western Force … it's about everyone who is going to play rugby in this state.

"I want the kids to be able to play up to someone, play for someone and play for their state, because that means something special."

Hodgson said the Force were far from dead.

"The fight's not over. Like all good West Australians, we'll go down fighting, we'll go down swinging," he said.

"They don't know what united is because they left us out, but this is what united is … let's stay united as one."

WA Sports Minister Mick Murray also spoke at the rally, accusing the ARU of being "blind" and "dumb".

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