Reading originally agreed an undisclosed fee with the Eagles for the 28-year-old ex-Brentford man three weeks ago but Powell has been sidelined with a hamstring injury since the autumn and unable to prove his fitness.
The Royals would love to complete the deal, but are refusing to sign an injured player. With captain Adie Williams facing a month on the sidelines and fellow centre-back Steve Brown only just returning from injury, Steve Coppell ideally needs the extra defensive cover Powell can provide.
But with deadline day looming the club are preparing to pull the plug.
"We are keen to sign him but it's got to be right for us. We have to make a decision for our long-term benefit and at the moment we're not in a position to do it before next Thursday," said Director of Football Nicky Hammond, speaking to the Reading Chronicle.
Meanwhile, super striker Nicky Forster is hoping to be fit for Reading's crunch game with West Ham at the Madejski Stadium on April 3rd. An explosive atmosphere is guaranteed when Alan Pardew returns to the club and Fozzy, who has been bugged by a stomach injury for the past four months, is targeting the game as the one in which to launch his first team return.
The 30-year-old revealed that his post-op rehabilitation programme is going better than had been expected, making an April 3rd return a distinct possibility.