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Walmart customers in the US could soon have their groceries delivered by Uber drivers under a pilot to be announced by the US retail giant.

Chief executive Doug McMillon will unveil the partnership with car-hailing services Uber and Lyft at Walmart's shareholder meeting later on Friday.

The company said in a blog post that it expects the trial to start within the next two weeks.

Walmart already offers an online grocery delivery service in 13 markets.

Under the new partnership, Walmart customers can place a delivery online and a Walmart employee will then request a driver from Uber or Lyft, the blog post said.

The driver will pick up the order and deliver it directly to the customer's location. Customers will be charged $7-10 for the service.

The pilot will begin in Denver, Colorado and one other city, reportedly Phoenix, Arizona.

Mr McMillon told investors in January that the company would focus on being more nimble as it announced the closure of 269 stories globally.

The expansion of its delivery service will intensify competition with online retailer Amazon, which launched its Amazon Fresh grocery delivery business in the US in 2007.