Barca go to Champions League opponents Dynamo Kiev on the back of defeat to Atletico Madrid.
"We cannot be happy, but this does not take away the ambition we have," Koeman said. "Tomorrow is another game. We must take the opportunity to qualify. I am not satisfied as a coach because we have lost a lot of points, but I am optimistic. We are aware of our situation and the decisions we have made. Although I am not happy with the points we have.
"[LaLiga Santander and the Champions League] are two different competitions. With the calendar we have, we will be near the top by the end of the year. The Champions League is different, you have to win particularly the home games and score away.
"We want to go through to the group stage and we'll see which opponent we will face in March. I don't think it will be easier to win the Champions League."