Reports over the weekend suggested Diamond was ready to leave the SPL club after failing to agree a new deal.
"I spoke to Zander Diamond on Saturday. He came in and apologised about a report saying he was looking to move elsewhere," said Calderwood.
"He is still positive that he could stay at Aberdeen. I certainly don't get the impression he wants to leave this club. I know for a fact that he doesn't want to leave and if it was just down to me talking one-to-one with him then I would get him signed.
"It's when other people like agents come in to it that things become bit harder to sort out.
"I think they would all like to stay but it's not as simple as that. It is up to Willie Miller to take care of that with the finishing touches."