The 19-year-old centre-back wanted to return to Barcelona in the summer and told Manchester City that he will not be extending a contract that expires at the end of the season.
Manchester City rejected two offers for the defender and Barcelona eventually decided against paying more than they felt was fair for a player who will be available on a free transfer next summer.
Barcelona could revisit their interest in Garcia in January if Manchester City play ball, rather than waiting for next summer.
Garcia is keen on the move, but Koeman conceded he does not know whether Barcelona will sign the youngster in January.
The Dutchman insists that any potential deal will depend on whether Manchester City are willing to compromise.
Koeman told Spanish daily Mundo Deportivo when asked whether Barcelona will sign Garcia in January: “Well, I don’t know.
“It depends on Manchester City.”
Garcia will be free to sign a pre-contract in the winter window with Barcelona with a view to a summer move, which could put further pressure on Manchester City to sell in January.