The Mexican club claims that the Blues are close to signing the 21-year-old winger, who had a two-week trial with Manchester United last year.
The 21-year-old winger had a two-week trial with Manchester United last year but the club decided not to pursue its interest.
Damm would not require a work permit as he has dual Mexican-German nationality and Fassi admits talks over a potential deal are imminent with Chelsea.
"Chelsea are the club interested, but we have to see how much they are interested. We can't go ahead of ourselves, we have to wait and see," Fassi told Medio Tiempo. "When it comes to us, it's a matter of sporting project. We want him to stay and we will see how much Chelsea are interested.
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"There is a belief that they arrive in Mexico on Thursday to talk with us. In principle we have a sporting plan for Jurgen and we hope he stays, but if something comes up from abroad, we have to take it into account and if it's serious, we have to respond. We will have news in the next 48 hours."