The world’s largest retailer Walmart Inc and logistics firm Deliv have reportedly ended a key same-day delivery partnership, due to a setback in the retailer’s race against Amazon to deliver groceries to customers’ home.

As per trusted sources, Walmart began strengthening its partnership with third-party courier firms in order to deliver products to customers in 100 US cities in 2018, post its failure to use Lyft and Uber for delivering groceries and struggling to use its own employees to deliver goods.

Deliv drivers had to usually wait for 40 minutes or more after they arrived at the store to collect orders, sources familiar with the matter claim. One of the primary reasons for this was that Walmart gives more importance to in-store customers over delivery drivers during regular hours, and this complicated the partnership, stated sources.

Reportedly, Deliv, which was one of Walmart’s initial partners with its pilot program in Miami and San Jose, gave a 90-day termination notice, and the two companies stopped serving each other in late January. The retailer confirmed the previously unreported decision and mentioned that it’s still partners with seven other delivery firms including Postmates and DoorDash.

Walmart’s store operations were a huge problem, plus the retailer was unable to process online grocery orders fast enough, said sources equipped with the knowledge of the matter.

Molly Blakeman, a spokesperson for Walmart, stated that the two companies have mutually consented to end the partnership. The intent behind every pilot program is to learn and Walmart concluded that although Deliv is a good delivery option, it is not the best fit for the company’s program, Blakeman said. Moreover, same-day grocery delivery is presently available in 800 of its over 5,000 stores and warehouse clubs in the U.S., with plans to add 800 more this year, Blakeman noted.

Last year, Deliv raised $40 million in a financing round from investors including United Parcel Service & Alphabet’s Google, and partnered with 20 new U.S. retailers as well, reported sources.