April 7 (Reuters) - Apple has been encountering setbacks in the engineering test phase of its first foldable iPhone, which could lead to delays in its mass production and product shipment schedule, Nikkei Asia reported on Monday, citing sources. 

Here are some details: 

* Engineering development issues could delay the firstshipments of the foldable iPhones by months in a worst-casescenario, according to the Nikkei report. * "It's true that more issues than expected have emergedduring the early test production phase, and additional time willbe needed to resolve them and make necessary adjustments," thereport said, quoting one source familiar with the matter. * However, Bloomberg News reported on Tuesday that Appleremains on track to release its first foldable iPhone inSeptember, alongside the iPhone 18 Pro and Pro Max. * The timing is not final, as the release is still nearlysix months away and production has not fully ramped up yet,according to the Bloomberg report, which cited people familiarwith the matter. * Reuters could not verify the reports independently. Appledid not immediately respond to requests for comment on thereports. * Apple shares were down 2.7% in afternoon trading. Theyfell as much as 5.1% earlier in the day. * Nikkei had reported in January that Apple would focus ondelivering its first foldable iPhone and two non-folding modelswith upgraded cameras and larger displays for a flagship launchin the second half of 2026.

(Reporting by Anusha Shah in Bengaluru; Editing by Sherry Jacob-Phillips and Maju Samuel)