's Alexa Fund and Tencent have invested $300 million in Andy Rubin's new smartphone company Essential, according to The Wall Street Journal.

For Amazon, it's the second major effort to back a smartphone. The company had a high-profile failure with its own smartphone, the Fire, which was launched with much fanfare in July 2014, but didn't make a dent in the overall smartphone market.

Andy Rubin co-founded Android before he sold it to Google. The first Essential smartphone was announced in late May and was promised to ship in June but still hasn't made it to market. Essential hasn't said when the phone will launch, only noting yet again that it's due out "in a few weeks" and will be sold by Amazon and Best Buy.

It's not clear why Amazon and Tencent are investing in the company which has had a rocky start, losing its vice president of marketing, head of user experience and head of communications all before the smartphone's debut. The investment from Amazon's Alexa Fund suggests Amazon is working to get its voice assistant pre-installed on the device.

"Essential Products has a compelling vision and roadmap for connected devices that integrates voice technology in novel ways," Amazon told CNBC. "We are excited to see Alexa become part of that vision where interacting with technology is simple, helpful and creates an interface that others can build on and innovate. We look forward to what will come from this collaboration. " A request for comment from Tencent was not immediately returned.

Despite executive departures, Essential faces an uphill battle in an already-crowded U.S. smartphone market dominated by Apple and Samsung. Established players, including LG, HTC and Lenovo's Motorola Mobility have had a hard time maintaining considerable share against the top two players.

Essential's first smartphone, named after the company, will cost $699 when it launches. Sprint is its only carrier partner in the U.S.

Other investors listed on the company's site include Redpoint, Playground, Access Technology Ventures, VY Capital, Altimeter Capital and Foxconn.

Read the full report from The Wall Street Journal.