Various reports had suggested Coyle was prepared to allow Cahill to leave for a substantial fee to fund his rebuilding plans for January as Bolton look to move away from the relegation zone.
However, Coyle insists he has no plans to cash in on the 24-year-old England hopeful, saying in the Daily Mirror: "We don't have to sell anybody to generate a transfer budget.
"I'm looking at Gary Cahill and I believe, if he shows the qualities he has, he can make the England World Cup squad. That's a motivation for him. He's a top player and hopefully we will see him at his very best here."
Chairman Phil Gartside says Bolton have constantly invested during transfer windows and has told Coyle that he can expect to be given funds.
"We have never, ever not backed a manager in the transfer window," he said in the Bolton News. "You go back over the history of transfer windows, we have always done some business, and it will carry on that way."
However, Coyle admits that a loan deal for Arsenal midfielder Jack Wilshere is unlikely to go through due to Arsene Wenger's current injury concerns.
"We obviously tried at Burnley, but with Arsenal's injuries it was put back," he said. "Now they've got other injuries there as well so he might not be available."