NEW YORK (AP) — Walmart says it will start farming out its delivery service. It plans to use contract workers, autonomous vehicles and other means to transport rival retailers’ products directly to their customers’ homes as fast as just a few hours. The nation’s largest retailer said it will dispatch contract workers from its Spark delivery network to merchants’ stores to pick up items and then bring them to shoppers. Over the past year, Walmart has doubled Spark’s coverage to more than 500 cities nationwide, providing access to more than 20 million households. Walmart aims to tap into its ties with local communities, particularly businesses in rural areas that have struggled to provide their own delivery services.