Martin Winterkorn, an ally of VW Chairman Ferdinand Piech, wanted to "assume responsibility" at Porsche, the carmaker that holds the majority of VW and was forced by debt woes to abandon efforts to seize full control of Europe's biggest carmaker, one source said.

The development is seen in the wake of the German carmakers seeking to forge an automotive juggernaut, two people familiar with the matter said.

The supervisory boards of both German carmakers were poised to address the issue at separate meetings on Thursday, one of the sources said. Winterkorn would succeed Wendelin Wiedeking, who is departing after losing a power struggle with VW.

Volkswagen's supervisory board is also set to approve the purchase of a minority stake in family-owned Porsche SE's healthy sports car business, Porsche AG, as a first step in integrating the two German carmakers.

Two VW supervisory board members told Reuters on Wednesday that Volkswagen and Porsche had broadly agreed details for a deal to combine two of Europe's most storied automakers.

Volkswagen is set to buy a stake of up to 49 per cent in Porsche AG in a first step toward creating an "integrated" automotive group by the end of 2011.

Analysts value Porsche's sports car business, which makes the famed 911 models, between 8 billion and 11 billion euros ($11.4-15.7 billion).