The Scotland international has been sidelined since last December due to a chronic bowel condition and has not yet returned to training.
Sir Alex Ferguson confirmed earlier this month that Fletcher will miss the start of the new season and that the 28-year-old has 'great challenges ahead'.
The situation has prompted suggestions that Fletcher will have to quit playing on a permanent basis, but the midfielder remains eager to return to first-team action.
"That's not really an option, I just want to keep playing," said Fletcher in the Daily Star.
"I know one day I will be back. I'm only 28 and want to give myself every opportunity.
"I've not started training yet, but I'm listening to the doctors and just taking my time. At the moment I feel like I'm capable of coming back."
Fletcher also revealed that United's priority this season will be to wrest the Premier League title away from local rivals Manchester City.
He added: "We'll try and win every cup we can but the main priority is the league. Obviously after Manchester City won the title we are determined to win it back."
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