Villa want to sign Johnstone on loan, and he looks set to become their number one stopper for the rest of the season.
Bruce appears to have been unconvinced by either of his two main goalkeeper options since taking charge at Villa - with both Pierluigi Gollini and Mark Bunn guilty of making errors.
Villa have made signing a new stopper one of their main priorities in January, and it seems that Johnstone is now edging closer to a move to the Midlands club.
Although Bruce admits that there is still work to do be done before the deal can be officially announced, the 55-year-old seems confident that the transfer will be completed before the end of the month.
“It's agreed verbally (believed to be a loan deal for Manchester United goalkeeper Sam Johnstone),” Bruce said.
“There's still a bit of work to be done. Believe me we're working hard, but as I've said many many times I will only improve us if the right one comes along.
“I'll make sure of that. I have to be patient for the sake of the club. We've gone in the past and bought too many too quickly and I wont make that mistake again.”
Johnstone has impressed at Championship level before, during a loan spell with Preston North End.
He has been kept at United so far this season, but he is yet to make a senior appearance for the Red Devils.