He said that the factors behind Pietersen being dumped would "become clearer soon" although whether that means the ECB will come forth before the October cut-off that both parties are believed to have previously agreed remains to be seen.
Cook was speaking at the Essex media day where it was expected that he would not discuss England matters, but he did respond when asked about Pietersen as well as Ashley Giles' position as favourite to be the new head coach.
When asked about why Pietersen was not considered part of England's future he said: "I can't answer that question totally at this moment in time which is incredibly frustrating for me," he told Sky Sports News.
"People will say I'm sitting on the fence, but there are a number of reasons that will become clearer soon but you have to respect the decision and the position I'm in at this precise moment in time. I know everyone will keep asking that question until we give the answers but at the moment we just can't and I'd love to talk about something slightly different if possible."
Pressed further before being allowed to move on to another subject he added. "If anyone thinks the decision was taken lightly, without a lot of consideration - a lot of things went into the decision. It was a tough decision, the decisions will be made clearer in due course and you just have to respect that. It is frustrating, but that is the position I'm in at the moment. It is what it is."
The short list for the role, with candidates due to be interviewed in the next fortnight, is believed to include Nottinghamshire's Mick Newell and the former England coach Peter Moores while the Daily Telegraph has reported that Trevor Bayliss is another candidate.
While 'big name' coaches such as Gary Kirsten and Stephen Fleming have not been attracted to the position, Cook said that England were "lucky to have the candidates we have."
"Gilo has had a tough winter, we have all had a tough winter, he's a very, very good coach, he's a fantastic coach. He's a good man as well," Cook said. "There are a lot of decisions to be made over the next few weeks, and important decisions as well. There are a number of candidates, we are lucky we can choose from a good number of candidates."
Cook does not have an official say in the final decision, but will be consulted and will speak strongly of Giles after their period working together with the one-day side. "It is an important relationship, you do have an input into it," he said. "You saw what a strong relationship Andy Strauss and Andy Flower had. Ashley is one of the favourites because he knows the system well and I've enjoyed working with him."
Cook conceded that the dismantling of England's Test side in Australia had been a surprise: there are potentially seven places up for grabs in the first Test team of the summer against Sri Lanka. The make-up of the 50- and 20-over sides will not escape scrutiny, either.
"That Test side which got us to No. 1, won three Ashes in a row, won't play again - it has broken quicker than any of us imagined. When the side breaks up there are places up for grabs. Any player who scores a lot of runs or take a lot of wickets will be up for selection.
"It's an exciting time for English cricket. It's a time where we have to look forward. It's been an incredibly tough winter, we can't hide from that. There are a huge number of reasons to be optimistic."
For anyone watching England collapse in Chittagong, or Sydney, optimistic probably was not the first word that sprung to mind.
Andrew McGlashan is an assistant editor at ESPNcricinfo