The Qatar Investment Authority could acquire more shares in ailing German sports car maker Porsche SE than previously thought, German magazine Focus said.

In an advance copy of an article due to be published on June 22, the magazine referred to details of a paper outlining the future ownership structure that it said Porsche CEO Wendelin Wiedeking had presented to the Porsche and Piech families.

It said there had been a provision for an external investor to hold 29.9 percent, when so far only a 25 percent share had been mentioned. However, there was no direct mention of Qatar.

Qatar has been discussing the possible size of a stake with Porsche and is due to reveal the outcome in two to three weeks, according to media reports.

Focus also said a Qatari delegation would discuss possible details with the state of Lower Saxony, which is home to Volkswagen. The state owns just over 20 percent of VW and has to approve any deals related to Porsche and VW.

Porsche amassed a 9 billion euro ($12.5 billion) net debt pile in its aborted attempt to acquire 75 percent of Volkswagen AG votes and has looked to rescue itself by uniting with its cash-rich subsidiary, which is Europe's largest carmaker.

Volkswagen CEO Ferdinand Piech is a member of the family that controls Porsche.

German car maker Daimler is also in advanced talks to buy a stake in Porsche, German magazine manager magazin reported on Friday on its website, citing financial sources.