The Brumbies are already eyeing revenge after booking their place in another Super Rugby AU title decider with a tense and drama-charged 21-9 qualifying final triumph over the Western Force in Canberra.

The defending champions will play the Queensland Reds in a rematch of last year's final after being forced to pull out all stops to end the Force's Cinderella run on Saturday night.

Making their long-awaited maiden finals appearance 16 years after entering Super Rugby, the Force had winger Toni Pulu red-carded after the halftime siren for a shoulder to the head of Brumbies centre Irae Simone.

The flashpoint no-arms tackle appeared totally unnecessary, with Simone already wrapped up by two other Force defenders.

Referee Nic Berry had no choice but to send Pulu off, leaving the Force a man short for 20 minutes.

But rather than fold, after Tom Banks swiftly punished the Force with a try from the resultant penalty to give the home side a 12-3 lead at the break, the underdogs dug deep to make the Brumbies sweat.

A second penalty goal from flyhalf Domingo Miotti to reduce the deficit to 12-6 was the only other scoring play while the Force toiled with only 14 men until midway through the second half.

Having swept into the finals on the back of successive wins over the Melbourne Rebels, NSW Waratahs and the table-topping Reds, the inspired Force had a clear game plan to disrupt the Brumbies' set piece at every opportunity.

It worked a treat.

Despite dominating territory and possession in the first half, the Brumbies were either bustled into error on attack or spurning penalty goal attempts in pursuit of tries.

Wallabies winger Tom Wright finally crossed in the 36th minute, after Miotti had opened the scoring a minute earlier with his first penalty, before Pulu's brain snap.

But not until replacement flyhalf Ryan Lonergan slotted a penalty goal seven minutes from fulltime did the Brumbies' slender lead ever look safe.

"It feels good. You never get bored of it," Brumbies coach Dan McKellar said of qualifying for the grand final.

"Super excited for next Saturday night. We're really pleased.

"This is the tough one to get through, against a side that had a bit of momentum and put us under pressure at times."

The Force were gutted to have fallen short.

"There's genuine disappointment there because probably when we reflect on that it was one that we let slip because we didn't fire too many shots," coach Tim Sampson said.

"It was a real arm wrestle for the full 80 minutes and unfortunately we just didn't get in any good attacking positions.

"It's going to sting, no doubt. I think the guys were pretty flat."

The Brumbies won last year's final 28-23 over Queensland but will enter next Saturday night's decider in Brisbane having twice blown healthy leads in two tight losses to the Reds this season.

"It would have been incredibly disappointing not to have got that third opportunity," McKellar said.

"I've said a number of times we've led (the Reds) for 156 out of 160 minutes (this year). There were just some critical moments there that we lost and they were good enough to take.

"But we'll see how they go next week when we apply a whole lot of pressure."