LOS ANGELES (BLOOMBERG) - The ride-hailing giant Uber Technologies is not a public company, but every three months, dozens of shareholders get on a conference call to hear the latest details on its business performance from its head of finance, Gautam Gupta.

Mr Gupta told investors recently that Uber's losses mounted in the second quarter. Even in the United States, where Uber had turned a profit during its first quarter, the company was once again losing money.

In the first quarter of this year, Uber lost about US$520 million (S$703.6 million) before interest, taxes, depreciation and amortization, according to people familiar with the matter. In the second quarter the losses significantly exceeded US$750 million, including a roughly US$100 million shortfall in the US, those people said. That means Uber's losses in the first half of 2016 totaled at least US$1.27 billion.

Subsidies for Uber's drivers are responsible for the majority of the company's losses globally, Gupta told investors, according to people familiar with the matter. An Uber spokesman declined to comment.

"You won't find too many technology companies that could lose this much money, this quickly," said Aswath Damodaran, a business professor at New York University who has written skeptically of Uber's astronomical valuation on his blog. "For a private business to raise as much capital as Uber has been able to is unprecedented."

Bookings grew tremendously from the first quarter of this year to the second, from above US$3.8 billion to more than US$5 billion. Net revenue, under generally accepted accounting principles, grew about 18 per cent, from about US$960 million in the first quarter to about US$1.1 billion in the second.

Uber also told investors during the call that it was changing how it calculates UberPool's contribution to revenue in the second quarter, which had the effect of artificially increasing revenue.

Uber's losses and revenue have generally grown in lockstep as the company's global ambitions have expanded. Uber has lost money quarter after quarter. In 2015, Uber lost at least US$2 billion before interest, taxes, depreciation and amortization. Uber, which is seven years old, has lost at least US$4 billion in the history of the company.