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Chelsea forward Hazard, 25, scored a superb individual goal in the 4-0 win over Hungary, but picked up a thigh injury and has missed training since.
"We are working on getting him 100% fit," said Belgium manager Marc Wilmots.
"I cannot give you a specific time when that will happen, nor can I tell you that he will be OK."
He added: "I really hope he will be able to train on Wednesday - but he still has some pain in his thigh."
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Wilmots' side, ranked second in the world, played Wales during their Euro 2016 and World Cup 2014 qualifying campaigns and have not won any of their past three meetings.
The last encounter saw Wales triumph 1-0 in Cardiff in Cardiff in June 2015.
Belgium winger Dries Mertens described Chris Coleman's team as "very good defensively", adding: "They give you the feeling you can score a goal but in the end they score a goal and have stopped you.
"If you don't play really well against them, you have a lot of problems. They also have a lot of quality up front."
Belgium are still waiting to find out if Eden Hazard will be fit for Friday's Euro 2016 quarter-final against Wales.