Valtteri Bottas will drive for Mercedes next season after agreeing to a new contract.

Bottas has signed on for 2019 with an option for a fourth season with the reigning Constructors' Champions in 2020.

The announcement of the 28-year-old's deal comes a day after Mercedes confirmed world champion Lewis Hamilton had penned a new two-year contract.

Having replaced Nico Rosberg following his shock retirement after winning the world title in 2016, Bottas won in Russia, Austria and Abu Dhabi as he finished third in the drivers' championship in his first Mercedes season in 2017.

He has yet to taste victory in 2018 but has four second-place finishes to his name. Bottas is fifth in the championship, 67 points behind leader Sebastian Vettel going into this weekend's German Grand Prix.

"It is great news that I will be racing for Mercedes in 2019 and it is nice to announce it here in Hockenheim – not just the home race for Mercedes but also the circuit where I took my first ever single-seater wins back in 2007," Bottas said.

"This year, with a full winter of preparation, I have been able to make a good step forward - and I believe that there is still more to come. We have not been so lucky in the races this year but the team knows how I am performing, and this is a great sign of confidence in me and my driving.

"I enjoy working with the team, and also being team-mates with Lewis – we have a good relationship, honest and straightforward, and always aiming to get the right results for Mercedes.

"We have a big battle on our hands right now, so it's good to have the future clear for everybody – it means we can have a full focus on the championship fight. Obviously, my goal is to keep performing at a high level - and to make it a no-brainer for the team when it comes to deciding their plans for 2020 as well."

Team principal and CEO Toto Wolff added: "We are very pleased to extend Valtteri's contract with Mercedes for another season at least - and to be able to confirm an unchanged driver line-up for 2019, ahead of our home race in Hockenheim. 

"Valtteri's performances have been excellent this season and, if not for our mistakes and his misfortune, he could be leading the drivers' championship at the moment. 

"When we took the decision in favour of Valtteri for 2019, it wasn't just about his undoubted speed and work ethic, but also a question of character. His relationship with the team, including Lewis, is open and trusting, without any politics at all.

"Those are the ingredients you need when you're fighting strong rivals in both championships and they mirror the values inside the team. I am very excited to keep Valtteri in the team and look forward to celebrating many more successes with him."