By Rick Carew and Mia Lamar 

HONG KONG--The Chinese homegrown competitor to Uber Technologies Inc. is enlisting big new investors including the private equity arm of Los Angeles-based money manager Capital Group Cos. in its $2 billion fundraising round, according to people familiar with the situation.

Capital International Private Equity Funds and Chinese insurer Ping An Insurance (Group) Co. of China are among the investors participating in Didi Kuaidi Joint Co.'s fundraising, which could value the Chinese ride-hailing startup at around $15 billion, according to these people.

Chinese ride-hailing startup Didi Kuaidi Joint Co.'s fundraising will be among the largest equity fundraisings for a venture-backed company in a single private placement, according to Dow Jones VentureSource. Didi's competitor Uber Technologies collected $2.8 billion in a fundraising round this year, while Chinese e-commerce giant Alibaba Group Holding Ltd. raised $1.6 billion in 2011.

Capital Group is best known for its American Funds family of mutual funds. The private-equity business focuses on emerging markets and has spawned six funds with total commitments of nearly $7 billion, according to its website.

China's ride-hailing market is a two-horse race. Uber last month started formal fundraising specifically for its China operation, UberChina. The U.S. company is also raising money from big Chinese fund manager Hillhouse Capital Group in a convertible-bond deal based on a discount to its future initial public offering price, people familiar with the situation said earlier. Beijing-based Hillhouse Capital, which is also an investor in Didi Kuaidi, is investing in Uber's global operations, not its local China operation.

Didi Kuaidi and UberChina, both of which spend huge sums on subsidies to entice drivers and riders, want to raise fresh capital to spend on luring traffic to their services. Didi Kuaidi's backers include Chinese e-commerce company Alibaba Group Holding Ltd. and Tencent Holdings Ltd. Uber formed a strategic partnership with Chinese search engine Baidu Inc. last year that included an investment in Uber's China operations. Uber's service in China uses Baidu's mapping and payments service.

Existing investors in Didi Kuaidi are also participating in the Chinese startup's fundraising and are likely to make up a large portion of the deal, according to people familiar with the situation. That strong demand, which Didi said in an earlier investor letter was oversubscribed in five days, could push the size of the fundraising round above its original target. One person familiar with the situation said the final size of the fundraising round could be as large as $2.5 billion.

Didi Kuaidi's daily private car-requests have tripled since May to 3 million-by its calculations, an 80% share of the Chinese market, it said in the investor letter, while it says its app is used for 3 million daily taxi rides, giving it nearly all of the taxi-app market. The company operates across more than 360 Chinese cities.

Uber chief executive Travis Kalanick said in a June investor letter that Uber believes it has captured close to half of the non-taxi ride-hailing market in China, with customers completing almost 1 million trips a day.

Neither set of figures has been audited by outside parties, and the uncertainty is deepened by the fast-growing nature of the market and the different metrics used by the two companies. To attract investor funds, both companies are jockeying to be seen as a leader in China.

Write to Rick Carew at rick.carew@wsj.com and Mia Lamar at mia.lamar@wsj.com

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