United plan to open contract talks with the Dutchman this month, and are wary of losing him for free when his big-money deal expires next summer.
But Van Persie concedes that he may not see out his career at Old Trafford: "It is not up to me. For the moment I am staying here for 18 months,” he told reporters.
"I can't look into the future. I don't know what is going to happen after that. We shall have to wait and see."
The striker also underlined his confidence in United manager Louis van Gaal, his former coach at international level with the Netherlands.
"I've known him for over two years and I know how he works," said Van Persie.
"Every year I still believe in him, we work together.
"We are trying everything we can to win games, but not only that, we want to do it in a nice way as well. That is a process and in that process we have to be honest and give everything we can."
