Amazon is thought to be developing a range of three smartphones with handset manufacturer HTC as it ramps up competition with Apple and Google.
The online retail giant is at an advanced stage of development, people familiar with the project said.
But one source told the Financial Times that the timeline for the launch has been changed, which could mean Amazon may decide not to release the devices.
Separately, Amazon is set to create 800 permanent jobs at its eight UK distribution centres before the end of the year, adding to its existing 4,500 employees.
Amazon, which has hired 15,000 Christmas workers in recent weeks, will offer temporary seasonal workers the chance to secure the jobs on guaranteed hours rather than zero-hours contracts.
The online retailer will also make changes to shift patterns at its distribution centres. Amazon will move from five-day eight-hour shifts to four-day 10-hour shifts, giving workers three days off each week.
Amazon operations director Catherine McDermott said: “Having recently reviewed and improved pay rates and overall compensation package, we are now moving to a four-day week which will provide employees with more days of free time and the potential for savings in terms of time and money.”