The Blues will host the Super Rugby Trans-Tasman final next weekend after a stuttering 31-21 win over the Western Force at Auckland's Eden Park.
Needing just a win to cement their place in the final, and secure home advantage, the Blues led 28-0 at halftime, all but sealing the fate of the Crusaders who had earlier beaten the Melbourne Rebels 52-26.
The result means the Highlanders will travel north this week for the tournament finale on Saturday night.
But coach Leon MacDonald cast a frustrated figure in the coaching box in the second half, as his side limped home, with the Force running in three converted tries to a solo Otere Black penalty.
The Highlanders will hold no fears of what awaits them at Eden Park having run the Blues close at the same venue in Super Rugby Aotearoa, before claiming a comfortable victory at home a month later.
A first-half try double from Hoskins Sotutu was sandwiched with five pointers for Dalton Papalii and Mark Telea as the Blues looked on course for a complete demolition of the Perth-based franchise.
But ill-discipline, poor option taking and woeful handling from the homeside allowed the visitors back into the match, and with just under 20 minutes to play they trailed by 28-14.
But Black's 65th-minute penalty stifled the comeback and despite losing replacement hooker Ray Niuia to a yellow card and a late try to former Irish international Rob Kearney in the final 10 minutes, the Blues hung on for an unconvincing 10-point win.
Blues 31 - (Sotutu x2, Telea, Papalii tries; Black 4 conversions, penalty goal)
Force 21 - (Kaitu'u, Kuridrani, Kearney tries; Prior 2 conversions, Miotti conversion) HT 28-0