Valve and HTC's Vive virtual reality headset will now release in April of 2016, HTC says.

In a Facebook post, HTC said the delay from the initial 2015 holiday season target was caused by continued work on both hardware and software.

"We have focused on developing immersive content, refining both hardware design and user experience, and building relationships with new partners both inside and outside of the gaming industry," the company said.

HTC's plan includes working with developers and designers "to create content that spans gaming, entertainment, medical, education and retail," through efforts including "hosting a developer conference in Beijing on December 18th, launching the second generation of the HTC Vive Developer Kit at CES and engaging audiences at key events including The Sundance Film Festival, SXSW, GDC and MWC.".

"We will be starting the new year by making an additional 7,000 units available to developers, followed by commercial availability in April 2016."

Announced back in March, the Vive is the most technologically ambitious of the impending first wave of VR headsets.

It features a complex positional tracking system that allows users to move around an entire room in virtual space (with in-headset guides to avoid users bumping into things), and custom controllers.

The Vive's two primary competitors, the Oculus Rift and PlayStation VR, are due out in Q1 2016 and the first half of 2016 respectively.