(Reuters) - Amazon.com said on Monday it is testing ultra-fast delivery of household essentials and fresh groceries in parts of Seattle and Philadelphia, as the company doubles down on efforts to grow its domestic footprint.

The service, called "Amazon Now", will deliver items including milk, eggs, fresh produce and electronics, in about 30 minutes or less, the company said in a blog.

The fast-delivery model is drawing interest from retailers as it is well-suited to single-item impulse buying - which is very attractive to consumers - as opposed to long-list grocery shopping.

The e-commerce giant said it is "utilizing specialized smaller facilities designed for efficient order fulfillment, strategically placed close to where Seattle- and Philadelphia-area customers live and work".

Prime members will get discounted delivery fees starting at $3.99 per order, compared with $13.99 for non-Prime customers. A basket fee of $1.99 will apply to orders below $15.

Amazon competes with Walmart+ WMT.N and Instacart CART.O in grocery delivery.

In August, Amazon started offering same-day delivery for perishable groceries to its Prime subscribers. The service was made available in over 1,000 U.S. cities, with plans to expand to 2,300 cities by the end of the year.

The Information had reported on Amazon's plan to offer ultrafast delivery in the U.S. earlier in the day.