ABU DHABI, UAE - Mercedes non-executive chairman Niki Lauda has responded to speculation about Ross Brawn's future as principal of the Formula 1 team by repeating his wish for him to stay.Brawn's position has been open to conjecture in 2013 when Toto Wolff took over as Mercedes motorsport head and the team signed Paddy Lowe from McLaren in a senior executive position.Mercedes declined to comment on media reports that Brawn had now decided to leave after the season-ending Brazilian GP but Lauda said it was "total rubbish".'MOTIVATE HIM TO STAY'Lauda said: "The situation is absolutely clear: I spoke to Ross a while ago and we agreed that he will come back to me after the final race of the season in Brazil to tell me whether he wants to stay or go."I am trying everything I can to encourage and motivate him to stay. I am the one who asked him to stay. I want him to do it but it is not my decision. If he stays. He will be team principal, nothing else or he will retire."Brawn is one of F1's most successful bosses, winning both the Drivers' and Constructors' championships with his own Brawn GP team in 2009 after previous owner Honda pulled out.He also masterminded Michael Schumacher's record seven titles with Benetton and Ferrari as a technical director and strategist.Brawn stayed on after Mercedes bought Brawn at the end of 2009 and survived management changes after Schumacher's three-year comeback with the British-based team ended disappointingly in 2011.'SUCCESSION PLAN'In January 2013, Brawn spoke of "a succession plan" and said he wanted to see how things went before making any long-term commitment to Mercedes.Brawn said: "It's rather like my succession plan at Ferrari. When I decided I was going to stop at Ferrari we built a succession plan and I am part of that, I've talked to Paddy, we know the situation."His position has evolved over the course 2013, without him giving any hints about the time frame for any departure. He told reporters: "There is a transition going on. We're just determining what will be the best timing for that. I want the team to be in the best possible place for 2014, so I think when the time is right we'll let everyone know what we're doing."The BBC said that sources close to Mercedes were saying that Brawn and Mercedes had failed to agree on a role in which he would have been happy to stay and that Lowe and Wolff would run the team in tandem.Sky TV commentator Martin Brundle said on Twitter: "Speaking with Niki Lauda last night he's determined to keep Ross Brawn at Merc if he can. That will take some doing to change Ross's mind."