Before Apple refreshed its iPhone line-up on Tuesday, Walmart wasted no time in announcing a trade-in programme for US consumers.

Starting on 21 September, consumers will have the opportunity to trade-in their old smartphones - like the now-discontinued iPhone 5 - at Walmart to receive immediate credit toward the purchase of a new smartphone. The programme, which is in partnership with CExchange, will launch at 3,600 participating Walmart stores and Sam's Club locations nationwide.

Walmart will offer store credit ranging from $50 (£32) to $300 (£191) for more than 100 working, non-damaged smartphones. Examples provided by Walmart include $300 for an Apple iPhone 5, $175 for a Samsung Galaxy SIII and $52  for a Samsung Galaxy S2.

Consumers just need to bring a working smartphone to an associate in the electronics department at Walmart stores or Sam's Club locations, where the associate will determine the trade-in value based on condition and specifications. Trade-in credit can only go toward a new, on-contract smartphone from AT&T, Verizon Wireless or Sprint at Walmart.

Read: Apple to start ‘iPhone Reuse and Recycle’ trade-in programme on 30 August

Just a couple of weeks ago, Apple launched the iPhone Reuse and Recycle programme. It kicked off on 30 August at select US Apple Stores but won't roll out to all Stores until early September. Apple limits trade-ins to work as a discount toward a new iPhone bought on contract.

Like Walmart, Apple determines the value of a trade-in based on the condition of the old phone. Many reports noted Apple's trade-in pricing for the iPhones is slightly below the competition. For example, an unlocked, undamaged iPhone 5 16GB is worth around $279, while an AT&T 16GB iPhone 5 is worth $255.

It appears Walmart has upped the ante with its $300 offering for an iPhone 5 - as that's more than what Apple currently offers. Customers looking to trade in other electronics like tablets, MP3 players, video games, cameras, laptops and more can go to "gadgets to gift cards" on Walmart.com.