The 34-year-old has struggled with a back problem for the last few years, but the former England international has managed to overcome the injury to play more regularly in the past 18 months.
Ferdinand's current deal expires in the summer and United boss Sir Alex Ferguson recently hinted the defender was in line for a new deal after hailing his form this term.
Former West Ham and Leeds ace Ferdinand admits the praise from Ferguson was a boost, but he wants to see how his body copes with the busy winter programme before making a decision on his long-term future.
"The best thing I can do is to look at it after Christmas, and then again in the summer, to see how I'm feeling and go from there," said Ferdinand. "But hearing the manager saying I could go on for maybe another two or three years definitely puts the spring back in your step.
"I will have a better idea about that in December or January time when the games start coming thick and fast. That is when it really hits you and you know the hard work has to start.
"I will probably then get a better gauge of where I am, fitness-wise, and the benefit of having the summer off then."