Busquets has a deal with Barca until 2023.
But he says: "I always said that I would not be a Barcelona player for 20 years, with a secondary role.
"As soon as I feel that my ambition is fading or that I will not be able to be physically level, I will leave this place. After, I cannot predict my future, but I am a big fan of the United States.
"There, football is growing and continues to grow. MLS is a competitive league and it really attracts me."