The unbeaten Sheffield fighter will face the South American on home turf at the Motorpoint Arena in October 20 with the winner taking the body's mandatory challenger spot.
Brook is under pressure to perform having struggled in his points win over Carson Jones last month.
Saldivia is ranked in the IBF's top five and has a 41-2 record, with 32 early wins, with Brook at 28-0 (18).
The victor will meet the winner of the all-American title clash between champion Randall Bailey and Devon Alexander in Texas in September.
"I proved I have massive heart against Carson," Brook said.
"I said after the fight that there needs to be an improvement and on October 20 my fans are going to see me at my very best."
Eddie Hearn, who promotes Brook, added: "We have a new team in place that is going to ensure Kell will hit new heights in this fight.
"It was always our goal to secure a mandatory position and now we are just one fight away from making that happen."
Victory over Saldivia will hand Hearn the chance to bring Brook's world-title challenge to Britain via purse bids.