According to Sky News, Apple is reportedly selling just 20,000 watches each day in the US – compared to the 34,000 iPhones sold every hour worldwide.
Data analysis firm Slice Intelligence said that just 4,000 units were sold on one day in late June.
This is in contrast to the 200,000 units sold each day during the week of 10 April, when it was first released.
Slice claims that Apple has only sold 2,000 of the luxury gold ‘Edition’ models of the watch, which cost £8,000 each.
The figures are not official, and are based on electronic receipts sent to email addresses by Apple.
Apple has not released any official sales figures for the watch, and is likely to group sales figures with products in its “other” category which include Apple TV, iPod and accessories in official reports.
In a research note to clients last week, Pacific Crest Securities said demand for Apple Watch was “slowing quickly”, and predicted it would struggle to meet initial sales estimates.
The Apple Watch has received mixed reviews, and initial sales may have been hampered by the fact that they were only available to buy online at first, rather than in-store.
But Apple has insisted that Apple Watch sales have “surpassed our expectations in every way.”