Costco is expanding its fast delivery network as it works to grow sales in new ways.

Earlier this week Uber said it would expand its partnership with Costco to deliver products in 47 U.S. states, up from 17 states. On Thursday DoorDash said it would also start delivering Costco products in the U.S. from all U.S. locations.

The moves mark an expansion of Costco's fast delivery network, as the membership warehouse retailer ramps up its e-commerce offerings. Costco has long partnered with Instacart to make fast home deliveries from its stores, using the service's network of contract drivers to outsource the service.

"Same-day delivery, powered by our third-party partners, has become a highly effective way to deliver more convenience to our members," said Costco Chief Executive Ron Vachris on a May call to discuss earnings.

Shares were flat in trading on Thursday morning.