Kimi Raikkonen will not race any further in 2013 for Lotus F1, according to the driver's personal manager Steve Robertson quoted by Finnish newspaper Turun Sanomat on Sunday morning.

According to the report, Raikkonen is to have surgery to address the serious back problems originally stemming from an old racing accident that flared up again in September and nearly forced the 34-year-old out of the Singapore Grand Prix.

The back surgery will take place this Thursday in Salzburg, and will leave Raikkonen out of action for at least four weeks of recuperation before he can start physical rehabilitation to prepare him for the 2014 season when he moves to Ferrari to partner Fernando Alonso.

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That means Raikkonen will not be able to participate in the final two Grand Prix events this year at Austin in Texas, US and Sao Paulo in Brazil. It will almost certainly cost him third place in the drivers championship where he currently has 183 points, only eight more than Mercedes' Lewis Hamilton in fourth with Red Bull's Mark Webber and Hamilton's team mate Nico Rosberg also within reach of overhauling the Finn in the final two races.

Turun Sanomat's report about Raikkonen stepping down from race duty for the remainder of 2013 was subsequently carried internationally by Reuters. BBC Sport received confirmation from Lotus F1 team boss Eric Boullier who said that he had learned of the situation only on Saturday evening, while Autosport also confirmed the story after speaking directly with Robertson who told the magazine that Raikkonen had pulled out "due to the severe pain." The driver has not been able to sleep in recent days without strong painkillers, Robertson revealed.

However the decision to call time on his 2013 season also comes immediately after a major public falling-out between Raikkonen and Lotus over unpaid wages for the season. Raikkonen said in Abu Dhabi that unless he reached an agreement and started receiving some of the back pay he was owed, he would not race again for the team.

It had appeared that the two parties had made progress in negotiations over the race weekend at Yas Marina and had reached an understanding to allow them to see out the remainder of the season together. Raikkonen was even quoted in the team's PR releases in the last few days as saying how much he was looking forward to returning to Austin for next weekend's penultimate Grand Prix of the year.

"After going there for the first time last year - like everyone - I'm particularly looking forward to this one," he had said. "I like the American atmosphere, it's just a relaxed environment. They know how to have fun, and most of all they love racing." Raikkonen added he'd selected to stick with the shorter wheel-base model of the E21 for the event.

Lotus team principal Eric Boullier told the media at the end of last week that "He [Raikkonen] is completely on side."

Boullier also insisted that: "We all spoke in Abu Dhabi to make sure we know where we're going - and how we're getting there - for the final races of the year. Our focus is first on a good performance in Austin, and then the focus becomes getting a good result in Brazil."

It's unclear exactly when or why the situation changed, whether it's at all related to the difficult financial situation or else if the back pain that Raikkonen has been suffering for the last two months suddenly worsened after Abu Dhabi. Alternatively, the decision to go for immediate surgery could be the result of a new medical evaluation and updated advice from his team of doctors warning him not to delay.

Most likely, Raikkonen is also anxious that leaving the surgery any later could mean that he might miss the chance to participate in the test session build-up to the start of the 2014 season with Ferrari, or even risk his participation in the first race of the year.

The team has since subsequently confirmed the story via a short press release. "Lotus F1 Team can confirm that Kimi Raikkonen will miss the final two races of the 2013 F1 season to undergo, and recover from, back surgery," the notice said.

"The team will make an announcement about the replacement driver for the United States and Brazilian Grands Prix in due course," it added.

The team's test and development driver Davide Valsecchi is the most likely candidate, much as J?r?me d'Ambrosio was called up at equally short notice for the 2012 Italian Grand Prix when Romain Grosjean was hit by a one-race ban for causing an accident at the start of the previous race at Spa.

What the decision to opt for early surgery and sit out the final races of the year will mean to Raikkonen's prospects of getting paid his outstanding salary for the year is also unclear.