BMW Chief Executive Oliver Zipse on Thursday said he would seek to strengthen bonds with Toyota and wants the current alliance between the German and Japanese carmaker centred on fuel cells and convertibles, going beyond 2025.

"In the next decades, we would do well to strengthen bonds," Zipse told the Automobilwoche Kongress on Thursday.

The alliance which currently includes a cooperation deal on fuel cell cars and joint development of a sports-car, should continue beyond 2025, Zipse said.

Fuel cell cars, which are powered by hydrogen, may benefit from a concerted push by policymakers, to industrialise the production of hydrogen, Zipse said.

Separately, Zipse said BMW is seeking ways to save costs by slimming down its portfolio of models.

"Coupes, convertibles and roadsters, we will see what will be left," Zipse said, commenting about one of the areas where BMW is reviewing its product offering.