The 32-year-old Spaniard will definitely take part in the Tour as well as the Giro d'Italia in 2015, but says he is not sure what 2016 holds in terms of his career.
Contador, who broke his Tibia in 2014, won the Tour de France in 2007 and 2009, the Giro d'Italia in 2008 and the Tour of Spain in 2008, 2012 and 2014.
He told reporters at a press conference: "I would like to retire being at the top. This year, I will definitely be competing and also next year. I cannot confirm it but that could be my last. Yes, beyond 2016, I don't see myself [competing].
"I don't want to put an exact date because many things can happen. Imagine that I fall in the Tour in 2016 then I would not like to retire in that way but right now I don't see myself competing for more than two years."
Contador added: "I feel very good. Physically I recover very well from training and I am really enthusiastic and happy with the team that I have around me. It's true that the years go by and although I feel really well, I don't know how many more years I could be competing in the great races and I don't want to reach that limit."
"My plan is to compete at the Giro and the Tour and I don't want to be second in either of them. I just want to win both although we have to wait and see what happens. Many people consider this challenge to win two Grand Tours impossible, so you can imagine three. I would only compete in La Vuelta this year if I have an accident in the Tour.
"I reiterate that I will only compete to win. I'm never satisfied. Victory is the only thing I think of."