The 32-year-old returned to team training last month, having been sidelined since breaking a metatarsal in September.
Neuer will not play in Bayern's last Bundesliga match of the season against Stuttgart, although he has not been ruled out of the DFB-Pokal final meeting with Eintracht Frankfurt.
The former Schalke man says he cannot risk rushing himself back into action simply to be certain of his place in the squad for Russia.
"I cannot say anything right now," he said at Bayern's official presentation of their 2018-19 kit. "I feel good with the things I am doing in training right now, but there's no forecast.
"I have to make the right decision for me, for the team and for Germany. It doesn't help when you're rushing this decision. I want to improve day by day and I try to regain my fitness as fast as possible.
"The steps that I already made were good and positive. I try to continue that way. Then, we will see if that is enough."
Oliver Schmidtlein, former Bayern and Germany physio, believes it is unlikely Neuer would be available until after the group stages.
"I think the earliest he could be involved is in the knockout stages of the World Cup," he told SportBild.
"Manuel won't be able to train in this situation, despite the time constraints, or he risks his recovery."
Sven Ulreich has deputised in Bayern's goal since Neuer's injury and has been tipped to make Joachim Low's World Cup squad.
Barcelona's Marc-Andre ter Stegen is likely to be Germany's number one if Neuer fails to recover in time.
Bayern Munich and Germany goalkeeper Manuel Neuer does not know if he will recover from a foot injury in time to play at the World Cup.
The 32-year-old returned to team training last month, having been sidelined since breaking a metatarsal in September.
Neuer will not play any part in Bayern's last two matches of the season, though, against Stuttgart in the Bundesliga or Eintracht Frankfurt in the DFB-Pokal final.
And the former Schalke man says he cannot risk rushing himself back into action simply to be certain of his place in the squad for Russia.
"I cannot say anything right now," he said at Bayern's official presentation of their 2018-19 kit. "I feel good with the things I am doing in training right now, but there's no forecast.
"I have to make the right decision for me, for the team and for Germany. It doesn't help when you're rushing this decision. I want to improve day by day and I try to regain my fitness as fast as possible.
"The steps that I already made were good and positive. I try to continue that way. Then, we will see if that is enough."
Bayern boss Jupp Heynckes confirmed Neuer will not play before the end of the season on Wednesday, telling Kicker: "Manuel won't play against Stuttgart, and not in the cup final."
Oliver Schmidtlein, former Bayern and Germany physio, believes Neuer would unlikely be available until after the group stages.
"I think the earliest he could be involved is in the knockout stages of the World Cup," he told SportBild.
"Manuel won't be able to train in this situation, despite the time constraints, or he risks his recovery."
Sven Ulreich has deputised in Bayern's goal since Neuer's injury and has been tipped to make Joachim Low's World Cup squad.
Barcelona's Marc-Andre ter Stegen is likely to be Germany's number one if Neuer fails to recover in time.
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