Lotus have confirmed Kimi Raikkonen will miss the final two races of the Formula One season in order to undergo surgery on a long-standing back problem.
The announcement brings an early end to Raikkonen's time with the Enstone-based team, the Finn having already signed a deal to return to Ferrari from 2014.
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 & will therefore miss the final 2 Grands Prix of the 2013 F1 season," the Lotus team said in a statement on their official Twitter feed, @Lotus_F1Team.
Raikkonen's manager Steve Robertson first broke the news in Finnish newspaper Turun Sanomat.
"The experts recommend surgery," Robertson said. "That will take place on Thursday in Salzburg, Austria.
"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 news brings about an untidy and unsatisfactory end to Raikkonen's time at Lotus, which began amid much fanfare at the start of 2012 but has deteriorated dramatically since it was announced he would be leaving for Ferrari at the end of the year.
Raikkonen was involved in an expletive-laden radio exchange with the Lotus pit wall during the recent Indian Grand Prix after failing to move aside for team-mate Romain Grosjean, and was then late arriving to last weekend's race in Abu Dhabi amid an ongoing pay dispute.
Raikkonen, who claims he has not been paid by Lotus 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, 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 won one race on his way to third place in the drivers' standings last year and also won once in 2013. Raikkonen's time with Lotus was marked by impressive consistency, with the 34-year-old racking up a record 27 consecutive points finishes across two seasons.
With the penultimate race of the season in Austin just a week away, Lotus will have to move fast to line up a replacement driver.
Sauber's Nico Hulkenberg and Williams' Pastor Maldonado head the list of drivers vying to replace Raikkonen in 2014, but it seems unlikely either could be released from their current deals at such short notice, leaving Lotus reserve driver Davide Valsecchi as the man in pole position to step in.
Raikkonen's official website posted a statement on Sunday evening in which the driver's management team expressed sadness at the situation.
"Kimi Raikkonen will undergo back surgery this coming week, the consequent four weeks' recovery time forcing him to miss the forthcoming United States and Brazilian Grands Prix," the statement read.
"Kimi suffered from issues with his back earlier this year at the Singapore Grand Prix and a reoccurrence of this problem has forced him to have surgery now to help prevent ongoing problems in the future, and to ensure he is at full fitness for the 2014 season.
"Kimi and his management are saddened that Kimi 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 received since the news has emerged."