LOS ANGELES—Labor shortages have cut into Amazon.com Inc.’s plan to make one-day delivery standard for members of its Prime loyalty club, delaying its bid to cement its lead in e-commerce and sending costs surging ahead of the all-important holiday season. The comments from the world’s biggest online retailer come as staffing emerges as a significant pain point for U.S. retailers, already battling supply-chain snarls, product shortages, rising inflation, and rocketing transportation costs. Seattle-based Amazon said it anticipates $4 billion in additional labor and related expenses during the fourth quarter, amid pandemic-fueled shortages that made it harder to hire warehouse workers and drivers, and forcing it to route packages to out-of-the-way warehouses with sufficient staffing. In April 2019, Amazon announced it would roll out one-day delivery for Prime subscribers, and it said that would cost the company $800 million in the second quarter of 2019 alone. Its race to faster shipping …