James McFadden wants to leave Birmingham following their relegation from the Premier League, his agent Willie McKay says.
The 25-year-old Scotland striker has been linked with a £5.5m move to Celtic and McKay said he wanted to play football at the "highest level".
"James has told me he wants to leave," McKay said.
"He is happy (manager) Alex McLeish gave him a chance to play first-team football, but it's a short career."
But Celtic have distanced themselves from reports that Birmingham have rejected an offer plus defender Bobo Balde for McFadden.
Sources at Celtic told BBC Sport they have not expressed an interest in McFadden.
It is being suggested that, while Aiden McGeady and Shunsuke Nakamura remain at Celtic Park, there is no need to pay a substantial fee for a similar kind of player.
City chairman David Gold said McFadden, who joined Blues from Everton in January for £5m, was "not for sale" and McLeish has also reiterated he would be at Birmingham next season.
"We want to keep our best players to help us get back to the Premier League as quickly as possible," Gold said.
Meanwhile, City have failed in a bid to sign veteran Czech Republic striker Jan Koller from FC Nuremberg.
606: DEBATEThe veteran, who played for Czech Republic in the Euro 2008 finals, instead appears set to join Russian Premier League club Krylia Sovetov Samara.
Blues had agreed an undisclosed fee for the 35-year-old with Nuremberg and were ready to offer Koller a two-year deal.
However, his country's record goalscorer has received a more lucrative offer from Krylia.
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