Cahill has long been linked with a move to a bigger club, in particular Arsenal, but Coyle is desperate to keep hold of a player he described as his "prized asset".
Coyle will speak to all of his squad members before the summer break to spell out his plans for the future and the Scot hopes it will be enough to persuade Cahill to stay where he is for the timebeing.
"There is no doubt he is unbelievable player and a prized asset," said Coyle of the 24-year-old.
"People will say I am biased but I look around and he is good enough to be in the England squad.
"For such a young age, and him being the top-scoring English centre-back in the country with pace and power, I don't want to lose him.
"I want Gary to help build on where we are. But I accept if someone comes in with an unbelievable £30million offer then we couldn't stand in his way.
"It would be the right thing for the club and the right thing for Gary.
"But my plan is to keep Gary here along with the rest of the ones I want at a football club and try to build a team.
"Most of them know my mind because I speak to them collectively and individually on a daily basis.
"I like to do that at the end of the season; sit down with them individually and say 'Listen, how do you think the season went? this is where I feel you are, I think you can improve here and there and this is our plans for looking ahead'.
"It is a natural thing to do, before they go away on their break and recharge their batteries, so they know the mindset I want them to come back with.
"It is fair to say over the next few days we will be sitting down with them."
Despite reports of a summer clear-out, Coyle insists every player has a part to play next season and he dismissed suggestions Sunday's match at home to Birmingham could be the last for a number of his squad.
"I'd be very surprised to say it was someone's last game at Bolton," he added.
"The players have been terrific. That (playing their last game) is not something I have even thought about."
Source: Team Talk
Source: Team Talk