Valtteri Bottas says he is still not sure where he will be driving next year but has underlined the importance of making the best decision for his long-term future in Formula One.

The Finn is expected to be retained by Williams next year, but ahead of this weekend's Malaysian Grand Prix no official announcement had been made. Asked by ESPN in Singapore if he knew where he would be driving next year, Bottas said: "I don't, but it's interesting. I feel positive about things and things are definitely developing. One thing is for sure, I know I am going to be racing, but which team is not sure yet.

"It's a fact that I am going to have new teammate whatever happens, but I can't say much more than that really. I'm pretty pleased with how things are moving forward."

Felipe Massa is set to leave Williams at the end of the year, with European F3 championship leader Lance Stroll expected to take his place. If Bottas joins Stroll it will be his fifth season as a race driver at the team, but he says it is important to think long-term about which team can offer a world championship.

"I think we've had some great moments with Williams together and I think we have more we can achieve together. We definitely want more and we want to win races together, so yes it would be nice. But of course you need to be aware of opportunities and think about your career in the long term, because I still have a lot of time in Formula One even though there are now a lot of younger drivers than me.

"I still feel that I am only going to get better and I still have ten years in front of me if everything goes well. It's all playing for the long-term plan and I need to win races and win championships and for that you need to be with the right team. Having looked at what opportunities there are, then definitely one option is to stay with Williams.

Mercedes, Ferrari, Red Bull and McLaren have all confirmed their driver line ups for 2017 and both Mercedes and Red Bull have their current drivers contracted until the end of 2018. But 27-year-old Bottas is still hopeful of breaking into a top team in the next few years.

"At the top at least for next year it seems quite closed, but who knows what is going to happen next year and what kind of places there are going to be or the year after next? You can't just predict those things and how they are going to go, so for me personally it is going to be massively important every race and especially wherever I will be racing next year will also be important for my future.

"It's Formula One and I wish I had a crystal ball to see what is going to happen, but you just have to keep pushing to get the good results."