Rosberg contract talks only in summer - Wolff

Toto Wolff says there is no guarantee Nico Rosberg and Lewis Hamilton will be paired together beyond 2016.

Rosberg, for a start, has a contract only until the end of next year.

"We will talk about an extension in the summer at the earliest," Mercedes team boss Wolff told Speed Week. "Until then, let’s see what happens."

Earlier, Wolff had warned that the bitterness of the feud between German Rosberg and world champion Hamilton cannot be allowed to spill into the team spirit.

Briton Hamilton has a longer contract than Rosberg, but Wolff admitted: "There are clauses in his contract, as is the case with all the other staff. In the case of damaging the company, for example."

But Wolff also told Salzburger Nachrichten newspaper that he has no problem with the rivalry at the moment.

"It will go on, with the two giving nothing to the other," he predicted. "But that’s good for the team because it makes our car faster."

As for the progress being made on Mercedes’ 2016 car-engine package, Wolff revealed: "We are on schedule. With the engine update we expect about two tenths per lap. And the car will also give us something."