Last week, the news site AllThingsD, part of the same company as The Journal, said Apple had scheduled a September 10 event to unveil the new smartphones as part of an effort to regain momentum.
An Apple spokesman declined to comment.
Apple's move comes with its chief rival Samsung reportedly set to unveil its own smartphones and other devices, including a smartwatch.
Speculation has centered around whether Apple will shift its strategy to include a lower-cost handset to appeal to more consumers, especially in emerging markets.
A survey released by Gartner last week said Apple's share of the smartphone market worldwide fell to 14.2% in the second quarter, while Samsung's share rose to 31.7%.
Gartner said the Google Android operating system was used on 79% of smartphones sold in the period.