BMW Motorsport boss Mario Theissen is hoping Sauber's future is resolved by the end of the year.

Although Theissen admits there is no deadline regarding a possible entry for Sauber in 2010, time is fast running out.

BMW's four-season foray in Formula One concluded with Sunday's Abu Dhabi Grand Prix, with Nick Heidfeld gaining a respectable fifth.

It leaves Sauber fighting to secure a place on the grid for 2010 because although the FIA are willing to include them as the 14th team, there is opposition, primarily from the likes of Williams.

If Sauber are unable to obtain 100% agreement from all the teams, it becomes a waiting game, hoping for another marque to fall by the wayside.

There remains speculation about the future of Toyota and Renault, but it is almost certain both will be in Bahrain for the opening race of next year in mid-March.

Then there are doubts about the new teams, Manor, Lotus, US F1 and Campos, and whether their plans will come to fruition.

Appreciably though, Sauber cannot wait indefinitely as they would naturally be ill-prepared for the rigours of what could be a 19-race campaign.

"Everybody says it's very likely another team will go, that we are unlikely to have 14 teams ready for next year, maybe not even 13," said Theissen.

"But that's all speculation at the moment. What we know is there's no unanimous agreement on the 14th team, so another team pulling out is the easiest way (to be in F1) from our perspective.

"Naturally the backers are keen to have a decision soon because you can only sign driver and sponsor contracts when you have a place on the grid, so they are pushing, together with us.

"There is no clear deadline on this, but obviously it becomes more difficult day by day.

"I don't think, though, we could leave it as late as mid-January. I hope it will be decided before the end of the year."

Theissen has also yet to make a decision on his future as there is a strong chance he would become team principal of Sauber should they survive.

For now he remains in charge of BMW Motorsport, with Theissen due to be in Macau in less than a fortnight for the final round of the World Touring Car Championship.

"My future is open," confirmed Theissen.

"I have the option to stay with BMW, or one of the other racing programmes.

"I deliberately pushed a decision out of my mind, and I will deal with it in the coming weeks.

"The top priority is to get a place on the grid for the team, and after that I will think about my own future."