Smartphone start-up Essential confirmed it secured an additional $300 million in funding, with Amazon’s Alexa Fund joining its growing list of backers.

Essential, founded by former Android chief Andy Rubin, has now amassed a $330 million war chest as it embarks on the ambitious goal of taking on Apple and Samsung in the premium smartphone segment.

The funding round was led by Access Technology Ventures, the venture capital arm of Access Industries, which bet $100 million on the start-up. Essential joins big names including Amazon, Facebook, Snapchat and Alibaba on the VC company’s books.

Other investors contributing to Essential’s funding round include Altimeter Capital, Vy Capital, Tencent and Redpoint Ventures.

In a statement released by Access Technology Ventures, Rubin said the investment group’s “global reach and long-term perspective match the scale and breadth of Essential’s ambitions”.

While Bloomberg first reported the company had raised $300 million in June, giving Essential a total value of almost $1 billion, at the time there was no confirmation of the report or mention of who the backers were.

Essential raised $30 million in 2016 from Rubin’s technology incubator Playground Global, Redpoint Ventures, Tencent and Foxconn Technology.

Rubin took the wraps off the company and revealed its first smartphone in May, but it is still unconfirmed when the device will become available.

However, in a tweet released yesterday, Rubin said: “We are in full mass production, ramping up to deliver your Essential Phone. Find out where you can get yours next week.”

The device, which was initially due to be released in June, will cost $699, but faces immediate competition from Samsung and Apple, which are both reportedly planning major smartphone releases in the coming weeks.

Apple will apparently unveil three new phones in September, while Samsung is expected to release its premium Galaxy Note 8 at a similar time.