Bayern Munich CEO Karl-Heinz Rummenigge has said Hamburg's decision to demote on-loan United States international Julian Green to their reserve side is "regrettable."

Green moved to Hamburg on a season-long loan in the summer but has been unable to force his way into the Bundesliga strugglers' first team, making just one start under previous boss Mirko Slomka and four substitute appearances under his successor, Joe Zinnbauer, while failing to make the match-day squad on several occasions.

Earlier this week, Hamburg sporting director Peter Knabel announced that Green had been demoted to the club's fourth-tier reserve team, leading the 19-year-old, who featured for United States at the 2014 World Cup, to respond on Facebook: "Nobody from HSV has spoken to me at all. I read in the papers that apparently I'm now playing for the U23.

"HSV took me on on the third day of the season to reinforce the first team. This was and is my aim, and is the reason why I transferred.

"I'm a licensed player, I haven't done anything wrong and I give all I've got in the training sessions. I always want to do my best to keep us in the league. If they let me play, I'll shoot goals."

Post by Julian Green.

Rummenigge said Bayern were also unimpressed with the situation.

"That's not what our intention was -- we send players on loan so that they can play at the highest level, and develop," he told Bild. "This not the case now. We can't and we don't want to 'stick our oar in' when it comes to the HSV coach's lineup. Nevertheless, the development is regrettable."

Speaking to his news conference ahead of Hamburg's trip to Bayern at the weekend, though, HSV coach Zinnbauer said it was "still not decided" whether he would be part of the first-team squad.

He added: "There were a few positive signs -- he is a bit angry and I want to see that. I hope he does not forget what he has to do to make the squad."