By Stephen English Updated with further quotes

Casey Stoner has admitted that his 2012 MotoGP title hopes are 'finished', following the announcement that he will miss this weekend's Czech Republic MotoGP in order to undergo surgery on his injured ankle.

The reigning world champion - who will retire at the end of this season - suffered a spectacular highside at Indianapolis last Saturday, which left him with fractures to his right ankle and severe ligament damage.

During a Honda press conference at Brno it was confirmed that Stoner, who returned to finish fourth in the Indianapolis race, will undergo surgery in the coming days following advice from doctors that a failure to do so could lead to permanent injury.

"I'm hugely disappointed for my team and all the guys around me. We've been waiting since Indianapolis for my doctor in Australia to receive the discs of the MRI scan and x-rays to fully understand the situation," said Stoner.

"The doctors in America were fantastic but I needed a specialist to study them and give me his report and explain exactly what's gone wrong.

"We were hoping that once they had seen the scans that it wouldn't be as bad as I first suspected and that we could race here, but in fact it was the opposite and a lot worse than first expected.

"We only found out at lunchtime today that it was game over but it seems this is our only option at this point."

The news that Stoner will miss this weekend's Czech Grand Prix has effectively ended his title challenge, since surgery will mean a lengthy recovery period. Stoner is third in the championship and 39 points from Yamaha's Jorge Lorenzo.

The BBC's Azi Farni (@AziFarniBBC) quotes Stoner as saying: "My plan is to come back a race or two before Philip Island."

Phillip Island, Stoner's home round, is the penultimate event of the series (October 26-28). Two races before would mean a comeback for the Japanese Grand Prix at Motegi, Honda's home race, from October 12-14.

However Stoner added: "Until we've had the surgery we won't know [the recovery time.]"

Stoner's accident was especially disappointing for the 26 year old, who had high hopes for a race won by his team-mate, Dani Pedrosa.

"It's disappointing that in Indy we had a good chance to get some points back [to Lorenzo] but now it's finished our championship."

Stoner, who has won four races so far this year, added: "We still have a season to complete and this isn't just me giving up, I want to get back to racing as soon as possible.

"I have a job to do and a career to see through to the end and for it to finish like this would be a disaster, so I'll be back as soon as I can to take part in as many races as I can before the end of the season."

Lorenzo holds an 18-point lead over Pedrosa with seven events to go.