The midfielder is having a scan on his knee which caused him problems during the 1-1 draw with Leicester City on Saturday.
"Aron has to have a scan on his knee and we have had to pull him out of the Iceland get-together," said Chris Coleman to the CT.
"I need to speak with Iceland because they want Aron to go across and report, which I find bizarre because we have had the diagnosis from the physio and the doctor and he's not fit to play, so he shouldn't really be made to travel all the way over there just to see the doctor for an hour and then come all the way back. "I will speak with Iceland and say that it is barmy."
Gunnarsson said: "I was supposed to go away but I got a knock on my right knee and have to stay for treatment. "I need a scan so I am not sure if I am going away.
"I keep getting a knock on it and I need to get it checked out so I don't do any more damage to keep me out later on in the season. "I need to be careful because I am still growing."