The Western Force is challenging its exclusion from next year's Super Rugby competition on the basis that its agreement with Australian Rugby Union does not expire until the end of 2020 and the national body has not acted in good faith by terminating it unilaterally.

The Perth-based team, backed by the billionaire mining magnate Andrew "Twiggy" Forrest, has vowed to fight the ARU's decision to axe it from the competition under an international agreement to reduce the number of teams from 18 to 15.

Andrew Forrest joins the crowd during a rally in support of the Western Force. Credit:AAP

Justice David Hammerschlag granted leave to Western Australian Rugby Union to appeal its axing in the Supreme Court on Wednesday, after it lost an arbitration earlier this month.

The hearing will be crucial to the future of the Perth side, coming a day after the ARU rejected an offer of $50 million from Mr Forrest to take on the financial burden of the struggling team.