Kiprop ran 3m 26.69s in Monaco last month, the fastest 1500m in 14 years, and he is the third quickest individual over the distance.
Willis has vowed to be more aggressive than normal and it will be a good test less than a year out from the Rio Olympics.
Fellow Kiwi Julian Matthews found the pace too hot in the second semifinal, finishing in 11th in 3m 40.45s - outside his personal best from Belgium in July of 3m 37.37s - and 16th overall.
"It's disappointing it ended that way but it has been a good championship for me and I've learned a lot from it," he said. "It would have been nice to have been a bit more competitive there at the end.
"I did everything I could. I just didn't have it and when you don't have it, you don't have it. It's a long last lap when you're off the back."
Matthews will have 10 days off to prepare for his last race in Italy, where he hopes to qualify for next year's Olympics.
Quentin Rew finished 10th in a personal best time of 3h 48m 48s in the gruelling 50km walk yesterday, cutting 94 seconds off his previous best and beating Olympic qualification by more than a minute. Rew kept to his own pace throughout, even though he picked up two red cards early in the race (athletes are eliminated after receiving three warnings for not having one foot in contact with the road).