Michael Schumacher says he still needs "a little bit more time" to decide if he wants to continue in Formula One beyond the end of next season.

Speculation over Schumacher's future has increased after Nico Rosberg signed a new deal at least until the end of the 2013 season. Schumacher said that he has yet to start negotiating with Mercedes because he wants to work out if the team is making enough progress, having yet to finish on the podium in any of his two seasons with the team since returning to the sport.

"I need a little bit more time to see about myself and how we are heading, and some input to see if that is what I want or not," Schumacher is quoted by Autosport. "It is more about how we maximise the potential of what we have made. It took some while to do so, talking about our general performance. You have to assess where you are and what needs to be done, and then to transform it. You would rather do this early than late, but we have to understand that we were later than we hoped to be."

Schumacher's first season with Mercedes came after it took over the reigning champions Brawn. However, he pointed out that Brawn's titles were the culmination of hard work put in previously, and that he would need to see evidence that the steps Mercedes has taken so far will be successful.

"It all comes back to what happened in 2009 to the team. And what happened in 2009 - even if it was a success story - it cannot be said this started in 2009. This goes well back two or three years before that. So everything in either direction has a lead time. The important thing is, are we on the right track? Did we take the right measures? And I think yes, but it has to be proven in the future."