Retail giant Wal-Mart Stores is racing to expand its e-commerce business with two new large-scale warehouses dedicated to fulfilling online orders and speeding up shipments.

A new 800,000 sq ft facility in Fort Worth, Texas began shipping orders last week, while the second, in Bethlehem, Pennsylvania is due to open in the first quarter of next year and at more than 1m sq ft will be the company's largest.

Combined, the new operations will house hundreds of thousands of items ranging from electronics, to toys, apparel, fitness equipment and sporting goods.

"With our dedicated online facilities and 4,100 stores within five miles of two-thirds of the US population, we gain a significant advantage by being positioned in the most important location - close to our customers," said Joel Anderson, president and CEO of Walmart.com. 

"This unique combination allows us to get more products to our customers faster and at a lower cost."

Wal-Mart says it expects sales from its e-commerce business to exceed $10bn globally this fiscal year - with online sales led by the US, but also generated in Brazil, China, and the UK.

However, this is just a fraction of the $466.1bn in total revenue booked by the retailer last year. 

As well as its two new online fulfilment centres, the company ships online orders from stores and many of its more than 130 distribution centres.

It is also planning to double the number of products available online to more than 5m this holiday season, including its own items and those offered through marketplace sellers.