Apple's long-rumored large-screen iPad Plus has been delayed. The device, which is expected to compete with Microsoft's Surface line and boost the company's languishing tablet sales, won't enter production until September according to sources familiar with the matter as reported by Bloomberg.

One person told the publication that the delay was related to supply of display panels. The initial plan was to start cranking out large iPads during the first quarter.

Tablet sales in general have slowed down around the globe, a phenomenon that Apple isn't exempt from. The Cupertino-based company recently recorded its fourth straight quarter of declining sales as the market is nearly saturated.

The tablet market is quite different from the smartphone industry. Many smartphone users replace their handsets every year to two for a variety of reasons. Some prefer to keep up with the rapid pace of technology while others look to replace a well-worn phone with something shiny and new. And because they're used on a daily basis, phones are much more likely to become lost, stolen or damaged beyond repair.

Tablet owners typically use their slates sparingly, often around the house to watch streaming movies or surf the web. Even that use scenario is being threatened thanks to do-it-all large-screen smartphones like the Galaxy Note 4 and the iPhone 6 Plus.

It's ironic when you consider the fact that tablets almost always cost less than smartphones.

Apple's iPad Plus is expected to carry a 12.9-inch display with the hopes of appealing to corporate users. It'll likely utilize speedier hardware under the hood but outside of that, little is known about the device.