The 20-year-old has impressed for the Mariners since joining the club last January, scoring three goals in eight appearances so far this term.
The Royals attempted to sign the Australia international in 2011 but the newly-promoted side failed to get the necessary work permit.
However, Brian McDermott now appears to be on the brink of capturing his long-term target in the January transfer window.
“We have been in discussions with Reading and both clubs are fairly satisfied with what’s on the table and now it’s up to Tom to reach a personal agreement with Reading,” said Turnbull.
“I am not going to say what the figure is but there is an agreement there. Of course we don’t want to see him go.
“I’d like to have Tommy here for another six years because he’s a special player.
“But the reality is that quality Australian players will always want to test themselves overseas where they can command the salaries and exposure they cannot command here.
“You have seen it with the Harry Kewells, Brett Emertons, Lucas Neills, Jason Culinas and so many more over the years.
“We could keep Tom here until May when his contract expires but then he could leave for nothing, and we as a club would be out of pocket. It’s a situation where our hands are really tied.
“The way things are now I would expect that things will be resolved by the end of the week concerning Tom and it may be that he will decide to stay, though considering his past association with Reading perhaps that would be unlikely.”
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