Valtteri Bottas admits it will be "very difficult" to win the world championship in the next few years if he stays at Williams.

Bottas is at the centre of the ongoing speculation about the 2016 driver line-up, with the Williams driver the favourite to replace Kimi Raikkonen if the 2007 world champion is not retained by Ferrari. Bottas has a deal with Williams until the end of 2016 but could be bought out by Ferrari if it decided to part company with Raikkonen.

At Silverstone, Williams was a match for Mercedes in the dry and its pace led Rob Smedley to say the team is now clearly ahead of Ferrari as 'best of the rest'. However, with limited resources compared to its rivals and a Mercedes customer engine supply Bottas thinks winning a title at the Grove outfit is unlikely.

"Williams has been many times world champion, I've always said there's no reason why they couldn't do it again, but the fact is at the moment it's very difficult," Bottas told F1i. "There are teams with much bigger budgets as everyone knows. Mercedes is dominating, now Ferrari are a bit ahead of us at the moment so it's not easy at the moment, but I'm not going to say it's impossible."

Bottas has been careful not to talk too much about the Ferrari speculation, insisting his management team are in control of his future. He says his current focus is on improving the fortunes of Williams, though he also admits he is wary of the need to make smart decisions when considering his future.

"In Formula One things can change quickly and if there are opportunities sometimes maybe you need to go for it, but for sure you also need to be in the right place at the right time. Wherever you are, whether you've been somewhere for a short time or a long time, for me it's always going to be the case that I'm going to do everything I can for the team and improve the car.

"So for me it's no different if I'm somewhere for three years, ten years or one year, I'm still going to do everything I can to help the team and get the best result."