Apple's new 4-inch iPhone, dubbed the iPhone 5se, and the new iPad Air are expected to go on sale on March 18, just three days after the company announces the products at a press event.

Sources told 9 to 5 Mac that Apple is unlikely to offer pre-orders for the new devices, but warned that plans could still change. The company doesn't usually release new iPhones so quickly after revealing them; it often waits one or two weeks, and there is usually an online pre-order period.

The 4-inch iPhone 5se will be Apple's 'budget' offering. Its body will be very similar to 2013's iPhone 5s, but it is rumored to sport a slew of improved features, including an A9 processor, a NFC chip for Apple Pay, support for always-on Siri activation, and the ability to take Live Photos

Apple will be hoping the 5se will appeal to those people who want modern iPhone features without having to buy the larger and much pricier 6s and 6s Plus. It will also help bring technology such as Apple Pay to more consumers.

The iPad Air 3, which is rumored to be launching on the same day, is said to feature a 9.7-inch display and have a thickness of only 5mm. Not much is known about the resolution, but some rumors suggest it could be a 4K screen.

Additionally, the Air 3 is said to include a Smart Connector and will support Apple accessories, such as the Apple Pencil and Smart Keyboard. It's also thought to come with an 8-megapixel rear-facing camera and a 2.1-megapixel front-facing version, enhanced speakers, and a variant of the A9 processor. It's thought that Apple will sell the tablet for around $499 in the US.

Apple still hasn't officially announced the March 15 event, where it's also said to be revealing new Apple Watch models, but it will probably confirm the date after Mobile World Conference finishes next week.