Storm winger Marika Koroibete, pictured playing against the Warriors, is being pursued by the Rebels and the Australian Rugby Union.

Melbourne Rebels could announce the defection of Melbourne Storm winger Marika Koroibete as early as next week.

Rebels coach Tony McGahan said he hadn't had any confirmation of Koroibete's signing and talks were ongoing.

But it is understood that a joint offer from the Rebels and the Australian Rugby Union was one the 23-year-old Fijian born winger cannot refuse as it's significantly higher than anything available in the NRL.

Koroibete will also be immediately available for Wallabies selection as he has lived in Australia for more than four years, with the national team coaches keen to bring him into their development camps once the Storm's NRL season finishes.

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The Rebels have made no secret of their chase for their neighbours' out of contract star and his signing will be a major boost to their attack, which hasn't been able to match the speed and running power of leading New Zealand and South African sides in recent years.

McGahan said on Thursday morning Koroibete's signing wasn't over the line.

"I haven't had any confirmation this morning but it's certainly ongoing and we would be hopeful of something being sorted sooner rather than later," McGahan said.

Koroibete is currently out with an ankle injury but has scored five tries this season and is a constant threat to break opposition defensive lines.

The Rebels could potentially field a backline including Koroibete, fellow Fijian winger Sefa Naivalu and power-runner Reece Hodge next season and it's a prospect both the team and supporters are savouring.

Koroibete will need to adjust back to the demands of rugby union but he's understood to have played both codes while growing up in Fiji and capable of regaining his union skills quickly.

The Rebels face ACT Brumbies at AAMI Park on Friday night in a game crucial to their finals hopes.