BEIJING, Aug 30 (Reuters) - BYD Co Ltd , a Chinese carmaker backed by U.S. billionaire Warren Buffett, plans to cut its sales force by about 70 percent, a Chinese website said on Tuesday, after the company reported a nearly 90 percent drop in first-half earnings, About 1,000 people in BYD's sales arm would be asked to resign initially, with the ultimate goal of cutting the headcount to 800, from 2,600, eeo.com.cn said on Tuesday, citing unnamed BYD employees.

Further layoffs in other departments were possible, the website reported said.

Several BYD executives contacted by Reuters either declined to comment or could not be reached.

BYD, 10 percent owned by Buffett's Berkshire Hathaway Inc , reported an 89 percent plunge in net income in the first half, lagging domestic rivals.

State auto group SAIC Motor Corp Ltd reported a 46 percent jump in earnings during the period, while Geely Automobile Holdings Ltd said net income rose 17 percent.

Xia Zhibin, head of the BYD's sales unit, resigned earlier in the month citing personal reasons. Analysts said slumping sales were likely to have played a part in the move.

BYD sold 259,915 vehicles in the first seven months, down 19.3 percent from a year earlier. (Reporting by Fang Yan and Ken Wills; Additional reporting by Alison Leung in Hong Kong; Editing by Chris Lewis)