The on-demand car ride service Uber lost at least $1.27 billion in the first half of this year, Bloomberg reported on Thursday, citing sources close to the matter.

As a private company, San Francisco-based Uber is not obliged to disclose details of its financial performance, however, it recently conducted a conference call with investors.

Uber chief financial officer Gautam Gupta led the call, during which it was revealed that the company lost $520 million in the first three months of this year and another $750 million in the following quarter, according to Bloomberg.

Uber did not reply to an AFP request for comment.

Uber has invested heavily as the ride-sharing service seeks to make inroads at home and abroad. The company is seen as a star of the "sharing economy," enabling people with smartphones to summon low-cost rides from motorists.

Uber has been valued at more than $60 billion, but has racked up losses at it expands and takes on competitors such as Lyft.

The prime cause of this year's red ink at Uber was believed to be a costly campaign in China with local rival Didi Chuxing.

Early this month, Uber announced that Didi Chuxing will take over its operations in China, ending a ferocious battle for market share.

In exchange for the Uber China assets, Uber and its Chinese partners will receive shares equivalent to 20 percent of Didi Chuxing, a statement said. 

Since Uber launched its China operations little more than two years ago, both companies have spent billions of dollars and traded vitriolic accusations as they fought for dominance in the potentially lucrative market.

As part of the merger, Didi Chuxing also took a stake in Uber, with reports saying it will invest $1 billion, valuing the US firm at $68 billion.

Uber has become one of the world's most valuable startups -- with operations in more than 50 countries -- but the company has faced regulatory hurdles and protests from established taxi operators in most locations where it has launched.