Nissan Motor Co. expects China to overtake the United States as the Japanese automaker's biggest market in terms of vehicle sales by 2022, Chief Executive Officer Hiroto Saikawa said on Thursday.

"We're placing strong focus on increasing sales in China by around 1 million units (by 2022)," CEO Hiroto Saikawa told Reuters in an interview.

"It would be difficult to sell the same number of cars in the United States by then."

Earlier this week, Nissan and joint-venture partner Dongfeng Motor Group Co. said they planned to boost annual sales in China to 2.6 million vehicles by 2022 from 1.5 million last year.