Lotus driver Kimi Raikkonen has expressed his sadness after he was ruled out of the final two races of the season because of injury.

The Finn, 34, is due to undergo surgery on a long-standing back problem in Salzburg, Austria tomorrow.

The news brings about an untidy and unsatisfactory end to Raikkonen’s time at the Enstone-based team, which began amid much fanfare at the start of 2012, but has deteriorated dramatically since he confirmed he would be driving for Ferrari next season.

Raikkonen was involved in an expletive-laden radio exch-ange with the Lotus pit wall during the recent Indian Grand Prix after failing to move aside for teammate Romain Grosjean, and was then late arriving to last weekend’s race in Abu Dhabi amid an ongoing pay dispute.

A statement on the Finn’s official website said: “Kimi and his management are saddened that he will not be able to complete the 2013 season with Lotus F1 Team where he was fighting for third position in the drivers’ championship.

“They would also like to thank all fans for the thousands of kind messages rece-ived since the news emerged.”

The Finn, who claims he has not been paid by the team all year, eventually raced in Abu Dhabi and only agreed to contest the final two grands prix after reaching an “understanding” with the team regarding payment of his wages.

Raikkonen will go under the knife in Salzburg on Thursday, ruling him out of the closing races of 2013 in the United States and Brazil.

“Kimi Raikkonen will undergo surgery on his back and will therefore miss the final two Grands Prix of the 2013 F1 season,” Lotus conformed in a statement.

“The experts recommend surgery,” added Raikkonen’s manager Steve Robertson. “The most important thing right now is to sort out the back problem.

“Then Kimi can go into next season in the best of shape.”

Raikkonen has been taking painkillers to control his back problem, which is believed to have its origins in a testing crash he suffered while with Sauber in 2001 and which flared up earlier this year, almost forcing him to miss the Singapore Grand Prix.

The Finn, who was world champion in 2007 during his first stint with Ferrari, spent two years away from F1 after leaving the Scuderia in 2009 but returned with Lotus at the start of last season.

He triumphed in one race on his way to third in the drivers’ standings last year and also won once in 2013.

Raikkonen racked up a rec-ord 27 consecutive points finishes in his time at Lotus.