Apple might soon launch an iPhone trade-in programme, allowing customers to exchange older models of the iPhone for a newer model at a discounted price.

Both 9to5Mac and MacRumors - citing unnamed sources - reported on Monday that Apple will introduce the scheme around the same time it  is expected to unveil the next-generation iPhone. Apple has even begun training Apple Store employees for the programme.

Read: Apple's first iPhone trade-in program to start this month?

Tim Cook, Apple's chief executive, has previously revealed that he is not opposed to an iPhone trade-in arrangement, as such an initiative could directly boost iPhone sales in Apple stores.

Bloomberg first reported in June that Apple planned to introduce an iPhone-trade in programme, with Brightstar, a mobile device distributor that runs AT&T and T-Mobile's trade-ins, spearheading the initiative. Apple would also allegedly sell the traded iPhones as low-cost refurbished handsets in emerging markets.

There's no confirmed launch date for the programme, but the unnamed sources are pointing to September.