GM Daewoo Auto & Technology has started mass production of six-speed automatic transmissions to help GM sell more efficient vehicles in Asia, company officials said on Wednesday.

GMDAT completed building the transmission production facility in Boryeong, about 190km (110 miles) south of Seoul, at a cost of 460bn ($US488m), the Yonhap news agency said.

The facility has an annual production capacity of 300,000 six-speed transmissions and 250,000 four-speed units. GM Daewoo chief executive Michael Grimaldi said he would double the annual capacity for six-speed transmissions by 2010.

To raise the capacity, GM Daewoo plans to hire 500 workers by 2012, the automaker said.

With exports accounting for most of its sales, GM Daewoo builds the majority of its vehicles for export to China, helping make Asia the most profitable region for the Detroit-based GM.

Unlisted GM Daewoo sold 960,186 units last year, 25.2% more than a year earlier, led by a 30% jump in exports. Domestic sales gained 1.7% to 130,542 units in the period, the company said earlier.