Both Chris Tremlett and Michael Carberry, who were a part of the England squad that were whitewashed in The Ashes by Australia during the winter, have recently insisted that Pietersen did nothing on that tour to deserve his omission.
However, Cook, who has not previously spoken about the situation, has stated that although he cannot reveal the logic as to why Pietersen has been banished right now, the "incredibly frustrating" scenario will become clearer in the near future.
"I can't actually answer that question totally at this precise moment in time, which is incredibly frustrating for me. Everyone will say I'm sitting on the fence but there are a number of reasons which will become clearer soon," Cook told Sky Sports News.
"You have to respect the decision, the position I'm in at this precise moment. Everyone is going to keep asking that question until we give the answers but at the moment we just can't, so I'd love to talk about something slightly different if possible.
"It is frustrating. If anyone thinks the decision was taken lightly and without a lot of consideration and a lot of thought... a lot of things went into the decision. It was a tough decision and the decisions will be made clearer in due course, and you just have to respect that at the moment. It is frustrating but that is the position I'm in at the moment and that is what it is."
Pietersen himself recently claimed on Twitter that he has had no contact with Cook or the ECB since his exclusion.