Guehi, 25, is out of contract at the end of the season, leaving Palace at risk of losing him on a free transfer at the end of the season. The club rejected a 35 million pounds bid from Liverpool last year but are now open to a sale this month should a significantly higher offer arrive.
Man City's interest has intensified after injuries to defenders Josko Gvardiol and Ruben Dias during Sunday's draw with Chelsea. Palace are understood to be seeking around 40 million pounds for Guehi, despite his contract situation.
Glasner said the club's preference is to keep the centre-back but acknowledged financial considerations could become decisive. He said there is a point at which the club would prioritise a transfer fee over sporting reasons, provided the player is open to leaving.
"I'm not naive," said Glasner, as reported by the Athletic and the Times. "If a massive offer comes from City and Marc wants to do it, it will happen."
Bayern Munich, Real Madrid, Barcelona, Inter Milan and Atletico Madrid are among the European clubs to have shown an interest in signing Guehi on a free transfer, and he can sign a pre-contract agreement with an overseas club from this month.
"If you're just valuing sports, everyone in the club will say Marc has to stay," Glasner added. "The chairman will tell you the same. But it's not one-dimensional. If you see the financial situation, it's very important.
"If somebody comes, there will be a moment when the club says 'now the financial issue is more important than the sports issue'.
"There will be a threshold where the club has to say it will happen - as long as Marc says 'I want to leave', because the final decision is always with the player."
Several European clubs, including Bayern Munich, Real Madrid, Barcelona, Inter Milan and Atletico Madrid, are also monitoring Guehi, who is free to sign a pre-contract agreement with an overseas club from this month.
Guehi has been a key figure for Palace since joining from Chelsea in 2021, captaining the side to FA Cup success last season and helping them qualify for European competition for the first time. Palace currently sit 14th in the Premier League and have reached the knockout play-offs of the Uefa Conference League.
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