Las Vegas - Huawei, China's largest cellphone manufacturer, is releasing a phone that can be thought of as the in-flight refuelling system of the mobile world: It can be used to recharge other phones.The Ascend Mate2 has a 15.5cm screen, slightly bigger than the already enormous Samsung Galaxy Note 3. It's almost the size of a tablet, giving rise to the term "phablet". It's the successor to a phone of the same size launched last year.The first Ascend Mate was not sold in the US, but Huawei CEO Richard Yu, speaking at a press conference in Las Vegas ahead of the opening of the International Consumer Electronics Show, said the Mate2 would reach US shores. He didn't say when or what it would cost. The phone is compatible with all US networks, but he didn't say which carriers would sell it.The huge size of the Ascend Mate provides space for a large battery, with roughly three times the amount of energy stored in an iPhone battery. Huawei claims it will last for 3.5 days of "normal" usage, or half that for heavy usage. Through a USB port, this battery can be used to charge smaller phones.Huawei Technologies was the third-largest cellphone manufacturer in the world in the third quarter of last year, according to research group IDC. However, it has few products on the US market, and is little known there. Huawei 's attempts to sell network equipment to US phone companies have been stymied by concerns that the company's products could contain "back doors" that allow for spying on US communications; an accusation the company denies.