Man Utd boss Ferguson to learn Van der Sar decision next month
Ferguson wants the Dutch goalkeeper to forget plans for retirement.
"I don't know his plans," said the United chief. "When you get to that age and have a young family, there are a lot of things to consider.
"It is usually sometime in December that he outlines his plans and how long he thinks he can go on.
"He is a very intelligent man, who understands his body better than anyone. He will come to the right decision."