Phillip Phillips Surgery POSTPONED

Phillip Phillips will NOT have kidney surgery today as scheduled, because he's burning up with a fever ... TMZ has learned.

As we first reported, Phillip has a serious congenital kidney condition that produces kidney stones so large they cannot pass. The condition has virtually debilitated his right kidney -- requiring 8 prior surgeries.

Phillip has had a flare-up through almost the entire "American Idol" competition, requiring a stent that was surgically inserted two months ago -- causing the singer extreme and continuous pain.

We're told Phillip now has a bad sinus infection that has triggered a high fever. As a result surgeons will not operate.

We're told the surgery has been rescheduled for early next week.