Didi Kuaidi, China's largest mobile-based car-booking company, added a designated-driver service to its platform on Tuesday, a move that is expected to ignite fierce competition in the growing transportation service sector.

Now worth an estimated $15 billion after its latest fundraising of $2 billion in early July, officials said the company will launch the new service, Didi Driver, in 10 major cities immediately, including Beijing, Shanghai, Guangzhou, Guandong province, and Xi'an in Shaanxi province.

It is scheduled to roll out in another 15 cities by the end of August and expand to cover more than 100 cities by the end of year, according to Cheng Wei, Didi's chief executive officer.