Peck bowed out after the emphasis shifted to the female lead. Various sources state that the role was then offered to Rock Hudson, Cary Grant, and Charlton Heston, all of whom declined.
The role was initially intended for Peck, but as the project shifted its focus toward a female lead, he stepped down.  Rock Hudson, Cary Grant, and Charlton Heston were then approached, but each declined the offer.