Arik Hesseldahl of BusinessWeek is allegedly in touch with a source who says the SDK for the two touchscreen devices will slip from its intended February release window by one to three weeks.
No justification is given for the delay. However, the progress of the development kit is described as "fluid" and may see Apple release little or no information about the programming environment before the end of February.
"There are, apparently, a lot of moving parts to something this complex," the writer claims.
The report claims authority based on past tips obtained by the magazine staff. The publication successfully leaked news of the SDK just a day before Apple chief executive Steve Jobs revealed official plans to open development to third parties in October.
Despite the delay, rumors have surfaced that the iPhone maker has been eager to spur development as soon as possible and may have released an early SDK to select developers, including a social networking site.