Sergio Perez has confirmed he is to leave McLaren at the end of this season.

Perez, who has been with the Woking-based marque for a year, informed his fans via an open letter on his Twitter account that the final two races in the United States this weekend and Brazil next would be his last for the team.

The news comes as no great surprise with reports earlier this week having suggested Perez was to be replaced by current McLaren development driver Kevin Magnussen from next season.

In his letter, Perez wrote: “First of all, I would like to thank McLaren for giving me the opportunity to be with them this season. It has been an honour for me to have been in one of the most competitive teams in the sport and I do not regret even a bit having joined them.

“I have always given the best of me for the team and still despite this I could not achieve what I aimed for in this historic team. I am committed to deliver very good results in these last two races, especially in Austin (the United States Grand Prix this weekend).

McLaren team principal Martin Whitmarsh thanked Perez for a statement he described as “kind and gracious”, as well as “for being a fine team member during the 2013 Formula One season”.

Whitmarsh added: “There are still two grands prix yet to run this year, and our collective focus is on scoring as many points as we can in those two remaining races.

“Checo has made many friends during his time at McLaren, and together as a team we intend to do our utmost to help him finish his year with us with two good results, especially here in Austin, where he has so many fans.

“We wish him well for the future, and are sure that he will have many successes ahead of him. As regards our driver line-up for next year, no 2014 deal has yet been signed with any driver except Jenson, and we therefore have nothing further to announce at this time.

“As and when that situation progresses, we will make a further announcement accordingly.”

Perez’s replacement, however, will be 21-year-old Dane Magnussen, the son of former F1 driver Jan, because although talks are ongoing, they are expected to be completed very soon.

McLaren are to promote Magnussen, winner of this year’s Formula Renault 3.5 Series, rather than retain Perez, following extensive analysis of performances.

Although McLaren produced one of their worst cars for many years this season, one that is set to complete the campaign without a podium for the first time since 1980, Perez has only scored 35 points to Button’s 60.

The 23-year-old has also been out-qualified nine times to eight by the Briton, a slender margin perhaps, albeit with Button renowned in Formula One for not being one of the quickest over a flying lap.

McLaren had hoped Perez would prove a reliable replacement for Lewis Hamilton, quickly moving to sign him last year following the latter’s departure to Mercedes.

Perez, however, has failed to show the promise suggested during his time with Sauber last season during which he notably scored three podiums, including runner-up in Malaysia and Italy.

Although Perez was fifth in India at the end of last month, matching McLaren's highest finish this year achieved by Button in China, the team have been underwhelmed by what they have seen.

In particular, time in the simulator of late has shown Magnussen to be quicker than Perez, and that has played a part in their thinking.

It means for the first time since Hamilton in 2007, McLaren are to promote an unproven driver into the big time.