A fee of £500,000 was agreed between the two clubs at the start of July, but Adam has previously admitted he was keen to fight for his place at Rangers.
Holloway told the Gazette: "I'll give him until Monday morning, then we'll have to rip up the offer we've made him.
"I've never waited this long for anyone before but I believe he's a talent. We need him and he needs us.
"But if the deal isn't done by the beginning of next week we will have to move on.
"I've seen the influence that Charlie had on the team and I've seen his character.
"He really believes in himself and his ability. If he was a chocolate bar, he'd be licking himself. He's got something about him that boy and I can't wait to work with him."