Gerhard Berger has said that the ball is in Mercedes's court over Nico Rosberg's negotiations for a contract beyond 2016.

There have been reports that the talks have hit a snag because while Rosberg wants a multi-year deal, Mercedes is only offering him a contract for 2017 only in order to leave the door open for Pascal Wehrlein's debut the year after.

"Everything is going according to plan," Berger, who is conducting Rosberg's negotiations on his behalf, told Germany's Sky.

"Both sides have the same goal - to see Nico at Mercedes for many years. There are only a few points on which we need to come to an agreement."

Mercedes team chairman Niki Lauda agrees that, amid the current talks, he is optimistic.

"I can reassure everyone," the F1 legend said. "The negotiations are going very well. In a relatively short period of time, everything will be done."

It is rumoured that, with Rosberg wanting three years but Mercedes only offering one, a two-year compromise contract is now being discussed.

"The ball is now in Mercedes' court," Berger confirmed to Germany's Auto Bild.

The former Ferrari and McLaren driver suggested that Mercedes would be wise to stick with Rosberg, given the less stable lifestyle enjoyed by the team's other driver, Lewis Hamilton.

"When you hear how many times he [Hamilton] jets between America and Europe between races, and think of the effort and energy that 1,000 people put into a race weekend, it is important that they have the perfect balance in the team," Berger told Bild am Sonntag newspaper.

"In Rosberg, they have an equally good driver from the sporting point of view and also highly reliable," he added.

There have been rumours that, should the parties not agree, Rosberg is open to speaking with Ferrari.