Clarets boss Sean Dyche wants England U21 centre-back Worrall and has made his move.
Forest have rebuffed Burnley's initial two offers in the region of £4million and £6m.
But the Greek-owned City Ground based outfit have not categorically dismissed selling their biggest asset if they get a bid of around £10m.
Meanwhile, Dyche has confirmed he wants to make defensive signings.
“There are a couple of things that are possible but I don't think they're probable," Dyche said of the transfer latest.
“The reason you can't say never is that things change quickly. You've got to be ready and flexible. It's not a no but not a probability.
“We've enough injuries to make us look at different possibilities. But we're not going to make signings for the sake of it. I believe in the players we've got."