Heidfeld made to wait for new BMW deal

The German driver has emerged as one of the main challengers to Ferrari and McLaren this year, but he is yet to secure his future, although Theissen said talks are progressing well.

"We are in positive discussions but it's not sealed yet," Theissen told reporters at the Hungaroring circuit.

"Don't expect anything during this weekend. It will probably be after the summer break."

BMW's possible line-up looks set to remain unchanged in 2008, especially following Sebastian Vettel's move to Toro Rosso to replace Scott Speed.

Vettel, who was BMW's third and reserve driver, was released from his contract with the German squad to race for Toro Rosso in the remaining races of the season.

Theissen says he expects the German teenager to stay at Toro Rosso in 2008.

"I expect that - but it's not for me to talk about," he said. "There is still a link between Sebastian and BMW. He will stay in our family but not in the F1 context. There is a clear separation. He is now with Toro Rosso in F1, but anything else he still has a link with BMW.

"I'm not even sure if he will continue in World Series - that is for Toro Rosso to decide. But with our motorsport people, he will be doing Formula BMW support."