The 19-year-old shot-stopper is highly rated in the USA and joined Chelsea last summer from MLS outfit Chicago Fire.
Chelsea immediately loaned him back to Chicago Fire last summer, where he impressed during his loan spell.
Slonina was part of Mauricio Pochettino’s pre-season squad this summer and made an appearance against Aston Villa
The London outfit decided to sign Robert Sanchez from Brighton in the ongoing window, which will leave Slonina down the pecking order in the Chelsea squad.
Belgian side KAS Eupen are interested in signing the 19-year-old on loan this summer.
And it has been claimed that Slonina is set to complete a move to the Belgian outfit today.
Chelsea and KAS Eupen are currently negotiating the final details of the deal before the player can sign a season-long loan deal.