The world’s largest contract manufacturer made a buyout bid to the subsidiary of Vietnam’s largest conglomerate, Vingroup, Reuters quoted two sources as saying.

But VinFast prefers a partnership since it is keen to brand itself as an eco-friendly automaker and wants to retain its electric vehicle business, one of the sources said.

In January, VinFast introduced three self-driving cars that are expected to hit the market later this year.

It tested autonomous vehicles in California in the U.S., one of the first foreign markets the company is eyeing.

Earlier this month it signed a memorandum of understanding with Taiwan’s ProLogium Technology Co. Ltd. for the production of batteries for electric cars.

VinFast plans to set up over 2,000 charging stations across the country this year to expand its electric vehicle ecosystem.

Vietnam’s first indigenous car manufacturer sold around 30,000 gasoline vehicles last year and expects sales of more than 45,000 this year.