Foster spent last season on loan at The Hawthorns and played an integral role in helping West Brom finish 10th in the Premier League.
He started every match in the league, bar the final day of the season when he was forced to sit out the 3-2 defeat by Arsenal due to injury.
The Baggies are now trying to bring the former England international back to the club, and sporting and technical director Dan Ashworth is hoping to settle on a suitable fee with Birmingham.
"We've started discussions with Birmingham City and we hope we can find a solution that suits them and suits us," said Ashworth in the Express & Star.
"If we can't, then no problem we'll have to move on, but it's down to discussions with them.
"As with every transfer, the selling club has 'X' in mind and the buying club only value at 'Y' so you hope that you find a tipping point that suits both parties. If you don't then the transfer doesn't happen."
Ashworth is not expecting any serious competition to sign Foster after Queens Park Rangers and Tottenham were also linked with the 29-year-old.
He added: "Ben hasn't suddenly appeared from Mars. He played 37 Premier League games last year and 38 the year before so he's been on everyone's radar.
"That's not a concern, he's been there for everyone to see and everyone knows where he is."
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