The 31-year-old is regarded as one of the best strikers in Europe.
“A man close to Manchester City called me some days ago to tell me of his interest in David,” Antonio Caliendo told L’Equipe.
“I believe the club are ready to put on the table a bid of more than 20million euros (£18.1m) to get him.
“Manchester City’s interest isn’t new. It happened last year.”
“A big Spanish club also contacted me a few weeks ago, before City did, as well as two clubs from the Persian Gulf,” he added.
“But David is untransferable and it is out of the question that I will talk more to these clubs since David still isn’t playing again.
“He will stay at Juve through this transfer window.”