The Australian Olympic Committee's signature is the only box still unticked on the 25-year-old's Tokyo passcard after Triathlon Australia announced Birtwhistle and Ashleigh Gentle's pre-selection for the national team.

The news was warmly welcomed by the world number six following a frustrating year.

After having the Olympics postponed, Birtwhistle missed an ideal chance to win a world title in Hamburg when a late announcement from the World Triathlon Series saw Oceania-based triathletes miss out on competing.

"It feels like a long time coming - this has been the dream since I was a kid watching the Olympics on telly and I always wanted to go myself," the 2018 Commonwealth Games gold medallist said.

"I started this journey a long time ago when I first started to get into the elite side of the sport and to finally be recognised and to get the nomination to be on the team is really exciting.

"It's a big weight off my shoulders moving forward - I don't have to worry about selection any more between now and Tokyo so I don't have to go chasing certain events, I can stick to my plan and make sure I get the preparation 100 per cent right."

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Set to turn 26 in January, Birtwhistle plans to spend most of the summer in Launceston before flying out of the country to rejoin his coach and training partners for the first time in nearly a year.

His pre-selection ends a long Olympic wait after the former Riverside High student narrowly missed out on winning selection for the 2016 Rio Games.

"I was pretty nervous the other day when I got the phone call," Birtwhistle said.

"Even though I know there's still more spots going to be announced for the triathlon team, it took me back to that moment when I missed out.

"But I'm a pretty different athlete to what I was back then - I was just coming onto the scene and didn't quite have the experience or the results behind me to qualify to that team.

"I've been confident for a while that Tokyo would be an Olympic Games I'd be at and everything that's happened this year has been a bit of a roadblock, so it's nice to have this to end off the year and hopefully it'll be a bit smoother sailing ahead of the Games."

Triathlon Australia's national performance director Justin Drew explained the decision to grant Birtwhistle and his Commonwealth Games mixed relay teammate Gentle, of Queensland, early selection.

"The philosophy of the [Triathlon Australia elite selection committee] is to strike a balance between certainty and preparation of the team across both individual and relay events, alongside ensuring we keep working to maximise quota, to refine strategy and drive performance outcomes," Drew said.

"Both Ash and Jake are proven performers at individual and relay, and I look forward to them preparing for success in Tokyo over the coming months."

The 2021 Olympic Games has been scheduled for July 23 to August 8, with the Paralympic Games to follow from August 24 until September 5.