The Waikato Chiefs will defend their Super 15 rugby title against Australia's ACT Brumbies in New Zealand after tense semi-final victories this weekend.

The Chiefs surged home with a 17-point burst in the second-half to down seven-time Super Rugby champions Canterbury Crusaders 20-19 in Hamilton, and will again host the final against the Brumbies next Saturday.

The Brumbies will play in their sixth Super Rugby final after snatching a dramatic 26-23 victory over three-time winners and favourites Northern Bulls with a try one minute from time in Pretoria.

While the Chiefs are bidding for back-to-back southern hemisphere provincial titles, the Brumbies, coached by former Springbok World Cup-winning mentor Jake White, will be chasing their third Super Rugby crown after earlier wins in 2001 and 2004.

It will be one versus three in this season's decider with the Chiefs finishing first and the Brumbies third overall, with the New Zealand team beating the Australians 29-22 in their only encounter this season in Hamilton on March 16. Overall the Brumbies lead 11-6 with one game drawn.

Should the Chiefs win next weekend it will be the 12th Super Rugby championship victory by a New Zealand team, while only the fourth by an Australian side should the Brumbies prevail.

The Chiefs, who beat the Crusaders 20-17 on the same ground in the semi-finals last year, were the underdogs going into Saturday's match, given the Crusaders' menacing lead-up form.

With Kieran Read and George Whitelock heading a marauding Crusaders forward pack they forced the Chiefs on to the back foot and led 9-3 at half-time.

The Crusaders continued to dominate in the opening plays of the second half to keep the Chiefs scrambling but when All Black ace Dan Carter missed a second penalty the Chiefs discovered their second wind.

In a golden 10-minute spell they piled on 17 points to lead 20-9 before they grimly held out a late Crusaders charge.

"We made it hard for ourselves with our set piece," Chiefs captain Craig Clarke said, adding their scoring blitz came from a change of tactics.

"We spread the ball more than we have done in previous weeks and they couldn't settle into their strong defensive system."

There was high drama late at Pretoria's Loftus Versfeld when Brumbies fly-half Matt Toomua sent outside-centre Tevita Kuridrani over for a try that had to be adjudicated by the South African television match official after the referee queried a possible forward pass.

Amid huge tension TMO Shaun Veldsman gave the 'green light' and inside centre Christian Lealiifano converted for a 16-point haul.

There was still time for the kick-off and a chance for the Bulls to equalise or even regain the lead, but they lost possession and the Brumbies kicked the ball into touch to end the game.

"I am extremely proud of the team as you cannot underestimate the challenge we faced taking on the Bulls in Pretoria," said Brumbies No 8 and skipper Ben Mowen.

"We did well during the first half, but knew the Bulls would come back after the break. Fitness was a major factor as we were well prepared to go the distance."

It was the first time the Bulls had lost a Super Rugby finals match at their Pretoria fortress. The Bulls were the last South African team to be Super Rugby champions in 2010.