McLaren's team principal Friday insisted that speculation over Lewis Hamilton's future was not a distraction in the fight for the world title -- and warned that the driver's next move might not be known for months.Martin Whitmarsh said McLaren had improved their performances since talk began about Hamilton, who has made it clear he is considering quitting the team after nearly 15 years.Hamilton has refused to answer questions on the subject at the Singapore Grand Prix, dashing hopes he would put an end to the speculation by announcing his decision.But Whitmarsh said Hamilton had successfully put swirling rumours to one side by winning two of last three races to lie second in the standings, 37 points off the lead with seven races to go."There's no question of putting a brave face on -- it's a question of focusing and doing a job," Whitmarsh said after the first day of practice at Singapore."We're concentrating on this year's championship. I think speculation on next year is something that we don't need to entertain or respond to. We're focusing on the here and now."Asked whether McLaren could wait to the end of the season before making an announcement, Whitmarsh smiled."We might wait until then, you never know," he said."I think that anyone who knows Lewis has witnessed... that he's very focused on doing the job. He realises this year that we have a strong opportunity to win a world championship."And I think we all realise that the right thing to do is focus on improving the car, don't make mistakes and maximise the points you can get from each race. I think that's what we're very much focused on."I know there's lots of other stories and speculation that fly around but I guess that's Formula One and I think we're content to get on with our job quietly."Whitmarsh admitted other teams would be queuing up to take Hamilton, who won the title in 2008 aged 23. But he described any suggestion the driver had already signed a deal with Mercedes as "fantasy"."I'm sure he'll want more money and I'm sure we'll want to pay less, that's how a business normally works," Whitmarsh said of the contract negotiations.He added: "It seems a long time because of the speculation people have made but once you sit down and seriously put your mind towards entering into a new contract, it doesn't take too long."Whitmarsh said it was "certainly doable" for Hamilton to overhaul Ferrari's Fernando Alonso and win the world title -- an outcome which would probably seal his signature for next year."Fernando's done a great job to be where he is and it's going to take some effort to overhaul him, but it's certainly doable and we're going to keep pushing him as hard as we can," Whitmarsh said.