The Belgian 18-year-old will go into the Under-21 squad once his reported £1.5million move has been completed.
"It is in the process of being completed," Martinez told the Liverpool Echo.
"He's a young, talented footballer who represents Belgium in the lower teams, in the Under-18s and has had good experience in going to France.
"He is a bright boy and we feel he is something different that we haven't got in the Under-21s so we are hoping he is going to be giving us something different in that group.
"We want a strong group. We have already got talented and very interesting footballers and I think David can fit in really well in that environment."
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